Video: Black box mystery: The Concorde crash

By Peter Greenberg Travel contributor
Dateline NBC
updated 2/1/2010 3:21:04 PM ET 2010-02-01T20:21:04

This report aired on Dateline NBC on Sunday, Feb. 22, 2009 at 7 p.m. ET.

The Concorde was called many things in its lifetime: sleek, sexy, supersonically sublime.

Ricky Bastin: It was the speed. It was the grace. It was the pace.

A magnificent flying machine that cruised at Mach two: twice the speed of sound. It was iconic -- even ironic. That needle nose -- retractable too. Those delta wings.

Mike Bannister: You could do things with Concorde clearly you can't do with other airplanes. Fabulous airplane to fly.

Poetry in motion. Elegance in action. And fast, fast, fast.

Christie Brinkley: It just made the world so much more accessible. It's always exciting to get to ny before you've left and do a full day's work.

It was a show-stopper. A name-dropper.

Joan Collins: There's lots of people like me, who love this aircraft

And almost always -- almost everywhere -- the Concorde was a crowd-pleaser.

During 24 years of commercial flying, the Concorde never had a single crash.... until Tuesday, July 25th, 2000. It was horrifying -- and utterly unexpected.

All told, 113 people died when the Concorde fell out of the sky and smashed into a small hotel in a Paris suburb. Something else died that day: a dream, a supersonic dream.

It's been nearly a decade since the Concorde crashed into that small hotel. But last year the accident made news once again, when French authorities accused a U.S. airline of playing a key role and charged it with manslaughter.  It was a highly unusual decision. And fiercely debated. Even today there are disagreements over what brought that plane down. Tonight we'll explore the theories about what really happened to Flight 4590.  And try to answer this question - until we know why 113 people died that day, will we be safe in the skies?

On that July day, the Concorde was full of German tourists on their way to New York.  The flight was delayed a couple of hours. When takeoff did begin -- at 4:42 in the afternoon -- other planes were asked to wait -- as they often were when the Concorde made a move. One of the planes on hold that day was a 747 -- with French President Jacques Chirac on board. At first, as the plane shot down the runway, all seemed normal -- but not for long.

Eyewitness: "I couldn't see anything, in fact - could only see a ball of fire."

Office workers near Charles de Gaulle airport, north of Paris, looked out their window -- as they did every day when the Concorde took off. The burning plane -- trailing flames -- lifted into the air. It missed the 747, with the French president on board by only thirty feet, its pilot would later say. The office workers watching nearby knew immediately that something was terribly wrong.

Drivers on nearby roads were watching --transfixed -- as the plane -- flying low and slow -- struggled to stay aloft. It tried to get up a little bit higher. And it started turning. And then suddenly -- the giant plane plunged to the ground. Video: Celebrities describe 'magnificent machine'

The Concorde had slammed into the Hotelissimo Hotel in the Paris suburb of Gonesse.

Alice Brooking: And my first reaction was that there'd been an earthquake.

Alice Brooking, a 21-year-old British student, was in her room in the hotel when the Concorde hit.

Alice Brooking: The walls were shaking, and the paintings were coming off the walls. They were falling to the ground.

She quickly realized there was only one way out of her second floor room alive -- through the window. She jumped -- and ran.

Alice Brooking: It was a scene from hell. It was absolute pandemonium. So people were literally all around me shaking.

Most of the passengers who died that day -- the German tourists -- were on a charter flight to New York. Once there, they were due to board a cruise ship. There was one American on the plane. And nine French crew members.

President Clinton: I wanted to extend the deepest condolences of the American people to the families of those who were lost.

Four more people died on the ground. Eyewitnesses who saw the blazing crash site through heat and haze were profoundly shaken. Few realized it then, but the crash was the beginning of the end for the world's first supersonic passenger plane.

French aviation investigators had a deadly mystery to solve. What could have happened? How could a supersonic plane without a crash to its name, with a highly skilled crew, on a clear afternoon -- suddenly smash into the ground less than two minutes after take-off?

When an Air France Concorde fell out of the sky in the summer of 2000 and crashed into a hotel near Charles de Gaulle airport, French air accident investigators were on the scene in minutes -- the accident happened -- literally -- in their backyard.

Peter Peter Greenberg: In aviation terms, you actually got to the scene when the plane was hot.

Paul Louis Arslanian: The plane was hot, indeed. Really hot.

Paul Louis Arslanian is the head of the BEA, France's air accident investigation agency.

Paul Louis Arslanian: Initially, the beginning of the investigation is always the same. Identify the wreckage. Protect any evidence. Find the recorders and so on.

But this was no ordinary investigation --because this was no ordinary plane. It was the Concorde -- a powerful symbol of French national pride.

Peter Peter Greenberg: You said it was a myth. It was bigger than life, wasn't it.

Paul Louis Arslanian: Yes. Concorde was called beautiful white bird, for example, nick-named.

Peter Peter Greenberg: And the beautiful white bird crashed.

Paul Louis Arslanian: Yes. And the beautiful white bird crashed.

But why? Somewhere in this scene from hell were clues that would help investigators determine what brought the Concorde down. All of France was waiting for answers -- and so was the rest of the world.

As it happened, investigators located the plane's black boxes -- its flight recorders -- almost immediately, while the debris was still smoldering.

Paul Louis Arslanian: To recover the recorders, one of our staff has to put an oxygen mask and-- goggles.

There were two recorders in orange boxes like these. One tracked flight data.  The other, the cockpit voice recorder, recorded the voices of the three-man crew. Back at headquarters, investigators got to work immediately.

They call this the reading room. And it was in this soundproof room, nine hours after the crash, that French investigators were able to listen to the last 90 seconds of a stricken plane.

French law prohibits the release of the cockpit voice recording after a crash.  But an official transcript of what was said in the final moments of Flight 4590 was issued. Dateline has recorded excerpts from that transcript: the words are real but the voices are not.

Investigators listened as the control tower warned the Concorde's crew that the plane was on fire. The first thing they learned was that the crew didn't know they had a serious problem -- until the tower told them they did.

Concorde zero four five nine zero you have flames, you have flames, behind you.

Second, they learned the flight engineer, the third crew member in the cockpit, decided early on that Engine two -- on the left side of the plane, the same side as the fire -- had failed. And after the plane was airborne, he confirmed that he'd shut that engine down.

Captain, are you shutting down engine number two there?

Flight engineer:

I've shut it down. Video: How the Concorde disaster unfolded

And finally they heard the crew struggling to get the landing gear up so the plane could get the speed and height it needed. But the gear wouldn't budge.

It was all over less than two minutes after takeoff. The cockpit voice recorder and data from the flight recorder gave investigators vital clues about when and why engine two was shut down. And about the landing gear that wouldn't retract. But the black boxes couldn't provide investigators with the one answer they wanted -- the catalyst. What set the accident in motion?

Peter Peter Greenberg: You really had a mystery to solve.

Paul Louis Arslanian: We understood very quickly that something happened. Just at takeoff. But why? It was not-- absolutely not obvious.

They searched the runway for clues and found pieces of a tire that had been oddly slashed. What they found next was even more puzzling.

Paul Louis Arslanian: It was a strip of metal which was twisted. It was typically not a part of the Concorde. And it had nothing to do on the runway.

Bob Macintosh: Indeed it looked like a piece of scrap.

Bob Macintosh, of the U.S. National Transportation Safety Board, was an accredited American representative to the Concorde investigation.

Bob Macintosh: We just didn't recognize immediately where that piece of metal might have come from.

But they did recognize that the piece of metal was important -- because it matched the slash in the tire.  It wasn't long before they identified the piece as an airplane part called a wear strip, a part that reduces wear and tear in the plane's thrust reverser as the plane slows down. But how did this bent strip -- this stray piece of metal -- get on the runway?

Paul Louis Arslanian: It appeared that it was a part which fall from another plane. So, the question was which plane?

They had another mystery to solve. They had to track the planes that had taken off in the hours before the Concorde. Which one had dropped that strip?

Paul Louis Arslanian: I had one investigator who spent a lot of time trying to find all those other planes and just have a look on them to see from where this part could have fallen.

Peter Peter Greenberg: So, he literally had to go chase planes?

Paul Louis Arslanian: It was-- a chase.

Attention soon focused on a D.C.-10 flown by Houston-based Continental Airlines.

Bob Macintosh: It came through Paris one day and-- a-- sharp investigator went out and he said, "I think I see the spot where that aircraft may have dropped a piece."

Once Macintosh was alerted, he called continental.

Bob Macintosh: I talked to their-- chief of safety. We found the location of the aircraft. It was-- it was making two or three stops and was gonna come back into Houston.

Macintosh and his French colleagues, along with representatives of the FAA, the U.S. Federal Aviation Administration, headed to Houston.

Bob Macintosh: We were standing on the ramp when it taxied in.

Peter Greenberg: You were waiting for that plane.

Bob Macintosh: We were waiting for that plane.

It was the very same DC-10 that had taken off five minutes -- and two planes -- before the doomed Concorde. They raced out to take a look, and they made a stunning discovery.

Bob Macintosh: Lo and behold-- it was very visible-- in-- in a micro minute. That wear strip was missing from that thrust reverser area. And it was a bit shocking.

Shocking, because on that Saturday morning in Houston, the investigators realized they were looking at a plane that may have inadvertently played a central role in the Concorde crash.

Bob Macintosh: And-- we opened it up-- took a look. We had some good dimensions from this famous piece that was locked up back in the evidence room in-- in Paris. But-- we knew it was a match.

It was a vital clue -- but was it enough to explain what had happened? Weeks after the crash, French investigators came to a decision. An agonizing one. Until they knew the whole story, the supersonic planes had to be taken out of the sky.

Paul Louis Arslanian: Facts were there. Everything was there. So something had to be done.

Three weeks after the crash --  Arslanian recommended the suspension of the Concorde's airworthiness certificate. It was an extraordinary step -- and it angered some of his fellow citizens.

Peter Greenberg: They hated you?

Paul Louis Arslanian: Yes. It was like a crime.

But his recommendation was accepted. France's six Concordes and the seven flown by British Airways would be out of service for the next 18 months.

With all those Concordes sitting on the ground, the pressure became even greater to figure out exactly how the crash happened -- and make sure it couldn't happen again. French investigators had months of work ahead of them. But when they did issue their final report, it would immediately ignite controversy.

After the crash of the Concorde in July 2000 -- and the decision to ground the supersonic fleet -- French investigators knew they had to work fast to figure out what had happened.

Paul Louis Arslanian: It was really not easy to do this, to work on this, knowing that every week people from the airline or the authority were askin’ the question, "Can we put it back into service?"

They had some tantalizing clues: Among them, pieces of a slashed tire and a bent strip of metal that matched. They also had lots of questions. Months of tests and analysis followed. The Concorde's tires and engines and fuel tanks were studied. Finally, after a year and a half, French investigators issued their final report. The description of the crash that follows is based on that report.

That day, the Concorde was cleared for takeoff at 4:42 p.m. It roared down much faster than a conventional plane, its tires under immense pressure. It was at this point that the wear strip -- that bent piece of metal dropped by the continental DC-10 which had so puzzled investigators -- played a critical role. Almost 40 seconds into the take-off roll, tire number two hit the strip.

Paul Louis Arslanian: The strip cut the tire. With the speed, the tire is peeled, really, like a potato.          

A chunk of tire, more than four feet long, slammed into fuel tank number five in the wing above, hitting with enormous force. And that tank was loaded with fuel.

Bob Macintosh: And it's under pressure. And it's full, full, full.

Tank number five ruptured -- in a completely unexpected way.

Bob Macintosh: It appears that the hit in one spot caused pressure in another spot that blew out a piece of the bottom of that wing.

Peter Greenberg: And that fuel didn't just come out, it came rocketing out.

Bob Macintosh: It was enough that it left a huge mark on the runway of unburned fuel in the moments when it first came out.

Fuel gushed out in torrents and ignited. Fire consumed the left landing gear assembly.

Paul Louis Arslanian: And we had a major fire -- eating the plane -- really eating the plane.

The plane veered to the left -- and by now French investigators say it was all but doomed no matter what the crew did. It was going too fast to abort takeoff --

Paul Louis Arslanian: If they had stopped the taking off, the fire would have just burst all around the plane.

But it was moving too slowly for an effective lift-off. Even so, the pilot took it up. The damaged Concorde got into the air -- but it couldn't accelerate. The crew fought to stay airborne.

Bob Macintosh: Things are getting very, very active in the cockpit at this point in time.

The power in engines one and two was unstable.  When an alarm went off in engine two, French investigators said the flight engineer assumed the fire was coming from that engine -- and shut it down.

Peter Greenberg: In retrospect, if the engineer had not shut down that engine, was the plane still flyable?

Paul Louis Arslanian: I can say that-- we tried to find any way out of this situation. There was no way out. There would have died differently, maybe. Maybe in a more terrible way. There was no way out of this situation.

The plane was flying too low -- and too slow. In the final seconds, as the investigators noted, the crew still struggled -- although they never knew exactly what had happened.

At 4:44 pm, after a flight that lasted less than two minutes, the plane pitched up and rolled and the beautiful white bird plunged into the hotel on the ground. At the heart of the investigators report? The role of the metal strip, dropped by the Continental DC-10.  By slashing the tire, they believed, that slender piece of metal set off the events that doomed the plane.

That wasn't all: Early on, investigators concluded the strip was a makeshift part made of titanium -- a metal not normally used for the strip. The fact that it happened to be lying in the path of the Concorde was, the investigators decided, a terrible coincidence.

Bob Macintosh: We don't know how it came off. But we know when we found it. It was looped around in such a way when the Concorde tire rolled over it, it was standing up like a knife edge.

Peter Greenberg: What are the odds of that?

Bob Macintosh: The odds are pretty far.

But once the tire and the strip connected -- French investigators came to believe -- Flight 4590 didn't stand a chance.

Peter Greenberg: Was Flight 4590 an accident waiting to happen?

Paul Louis Arslanian: Now that we know what happened, it was waiting to happen. But it needed so many extraordinary, impossible-- events to happen the same day at the same moment that nobody could have-- played a chance on it.

While French investigators believed they'd solved the mystery of how the crash took place, it would be years before French authorities decided to hold an airline accountable.  In the summer of 2008, they charged not Air France, operator of the Concorde, but Continental Airlines with manslaughter. The charges fired up the debate about what really happened to Flight 4590. That story may be far more complicated -- and frightening -- than French investigators reported.

In the summer of 2008, French authorities filed manslaughter charges against Continental Airlines -- and sent shockwaves through the aviation community.

But even before those charges were filed, there were questions -- and objections -- about the way the French had handled the investigation and about some of their conclusions. Many of the objections came from Britain -- home of British Airways, which flew seven Concordes of its own.

Mike Bannister: I'm not absolutely convinced that everything that could be found out has been found out.

Mike Bannister is the former chief Concorde pilot for British Airways. He flew the supersonic plane for 22 years, and loved it so much, he avoided using the autopilot.

Mike Bannister: We flew it by hand a lot because it was such a delight to fly.

After the crash, he served as a technical advisor to British investigators. But in France, most major air crash sites are treated like crime scenes. Because of that, Bannister says, the British team was allowed only a cursory look at key evidence.

Mike Bannister: I don't know what would have been found. But you-- you can never know what you won't find if you're not allowed to look.

Peter Greenberg: There's more to the criticism. The French report, you'll recall, said the accident was triggered by one event -- the wear strip -- dropped by that continental plane -- which sliced a tire. But air accident investigators and technical experts will tell you that a plane rarely -- if ever -- crashes for just one reason. But some experts think that in the case of the Concorde there wasn't just one reason -- there were at least half a dozen.

Mike Bannister: An aircraft accident on a complex airplane like Concorde is going to be multiple causes that tragically come together on one day in one place at one time.

Bannister says French investigators uncovered many of those causes -- but either ruled them out as causes -- or didn't connect them.

Mike Bannister: I think it's difficult to understand why certain things are not seen as part of this total chain of events.

The chain of events that brought down the Concorde -- say Bannister and others -- began even before the plane pushed back from the gate. That day, the German passengers on the charter were told they'd be delayed for a repair. It was nothing serious -- but it held up the flight for a couple of hours.

Peter Greenberg: Most charter flights don't leave on time. But this was the Concorde and time was of the essence. Flight 4590 was taking its high-flying passengers to New York to connect with their cruise ship and what was supposed to be a trip of a lifetime

In their report, French investigators referred to the crew's "firm desire to carry out the flight" -- but they said nothing about whether the pressure to be punctual influenced the crew's actions that day. Bannister and others believe it may have.

Mike Bannister: Particularly in a Concorde operation, one of the things we were always selling was time. Certainly, there were time pressures. And there were certainly other distractions.

For instance, the passengers had packed heavy for their cruise and the Concorde was overweight. On any aircraft, but especially the Concorde, weight -- and balance -- are critical.

Greg Feith: Because if the aircraft is overweight or its out of what they call CG, or center of gravity, that presents a real problem for operational control for the pilots.

Greg Feith is a former lead investigator for the National Transportation Safety Board. He has also worked as a consultant for Continental Airlines on a case unrelated to the Concorde. On the day of the crash, he says, the crew was warned by the flight dispatcher the plane was heavy -- but the crew knew the clock was ticking. Did they push the envelope?

Greg Feith: The crew knows that they're gonna be overweight because the flight managers told 'em that they had a weight problem, but knowing that information, they chose to try and operate the airplane under quote "normal" circumstances.

In fact the plane was even heavier than the crew knew -- because 19 extra bags had been loaded and never accounted for and all that weight may have made the plane less manageable.

Mike Bannister: It's possible that had the airplane been in the correct trim, with a little bit less weight, it may have been more flyable. They may have been able to accelerate and climb. And then that may have blown the flames out.

French investigators documented the weight problem -- but dismissed any role in the crash. But others who've read the report say that not only was the plane late and overweight, it was also over-fueled -- by more than one ton. That's especially important where Concorde's concerned.

Peter Greenberg: This plane has been described to me as a flying fuel tank.

Greg Feith: It is a flying fuel tank. Literally. You have people sitting on top of the gas tank.

While the tanks were full for the flight to New York, bannister and Feith believe that at least one tank -- number five, the one struck by tire debris -- was probably too full. And too pressurized. 

Mike Bannister: We looked at this shock caused by the piece of rubber flying up and hitting the tank. And it could not be reproduced unless the tank was 100 percent full.

Peter Greenberg: So when that tire hit, it had nowhere to go but out.

Mike Bannister: Absolutely. The additional pressure that comes from the big piece of tire debris hitting the tank forces the fuel into a shockwave situation and forces out a piece of tank skin.

In their report, French investigators acknowledged that the tanks were full. But not too full. And they did not address the issue of whether fuel tank number five was over-pressurized.

But Bannister and Feith say there was something else. Something important. The day of the crash, the Concorde was missing a part called a spacer. Its job was to keep the plane's wheels in alignment during takeoff and landing. But Air France workers had forgotten to re-install one in the left-side landing gear during routine maintenance.

Greg Feith: The spacer will be located down in this area. It sits inside the axel. And without that spacer, now these wheels are no longer rigid. And they're allowed to castor--

Peter Greenberg: So, instead of rolling like this, they're rolling like this.

Greg Feith: They're gonna be rolling on an angle. And when you roll that tire on an angle, all of a sudden now you compromise the integrity, of-- especially of the side walls and of the center tread.

In other words, those tires might be degraded. The spacer had actually been missing from the Concorde for four days.

Mike Bannister: Personally, I'm absolutely convinced it had some effect.

Peter Greenberg: Explain that.

Mike Bannister: Clearly it should be there as part of the design of the airplane. And not only was it not there for this take off, the aircraft had done four other cycles. Two take offs and two landings with it missing, so to believe that there wasn't some effect of that prior to this take off is, to me, difficult to comprehend.

French investigators, for their part, noted that the spacer was missing but concluded that it did not contribute to the accident.

The weather may have played a part too. Before takeoff, the tower told the crew the tailwind had increased to eight knots. Strong enough, bannister and Feith say, to dictate a change of runways or at the very least, a discussion. But that day, there was no reponse from the crew . Even French investigators couldn't explain the crew's silence. Bannister and Feith, for their part, speculate that pressure to take off -- to beat the delay -- may have played a role.

Mike Bannister: I believe it was a-- an unfortunate decision by the crew not to take more notice of the reported tailwind.

And finally, there was the state of the runway itself. One reason air travel is safe is because plane engines are so reliable. But they're also vulnerable to the debris left on any runway. The bits and pieces planes leave as they come and go. It's called FOD, or "foreign object debris".

On the day of the crash, one of the twice-daily runway inspections was cancelled. Would an inspection have picked up that metal strip? We'll never know. So critics of the French report say the chain of events that led to the crash started long before the Concorde left the gate.  They say Flight 4590 was delayed, overweight, over-fueled and a part was missing. The wind was up and the runway had not been inspected recently. None of these were major issues on their own. But together, critics say, they may have helped set the stage for disaster.

Greg Feith: I think when you look at accident investigation, you have to develop those facts and then connect the dots. In this case, they should've connected the dots and they didn't.

But there is another element in that chain of events, Bannister and Feith say -- another big one. And it was key to a near-catastrophe with eerie similarities to the Concorde crash at another airport more than two decades earlier.

Bill Lightfoot: I told her, "There's a hole in the wing. If you look here, you can see this: a big, jagged hole in the wing."

When French investigators filed their report on the crash of air France Flight 4590, they outlined a startling discovery: In the years before the crash, Concorde tires had burst or deflated 57 times, a rate much higher than conventional planes. The French recommended improvements to the tires, but still placed most of the blame for the accident on that metal wear strip found on the runway. But other aviation experts believe those past tire failures are key to understanding why the Concorde went down.

GregFeith: From an accident investigation standpoint, I'd be looking at that. There had to be a systemic problem.

The most serious of those tire failures took place at Washington Dulles international airport more than two decades before the Paris crash. The National Transportation Safety Board issued a report on it -- the NTSB’s Bob Macintosh remembers it well.

BobMacintosh: That was a wake-up call. That was a loud wake-up call.

In many ways, it was also hauntingly similar to what happened to air France Flight 4590.

On Thursday, June 14th, 1979, Air France flight 54 -- bound for Paris -- taxied to runway one nine, left for takeoff.

Bill Lightfoot was a passenger that day, seated in row 23, a window seat on the left -- about two thirds of the way down the plane.

BillLightfoot: I was looking out the window to keep track of the time. And I was gonna make note of when we took off.

Lightfoot was an aviation consultant. He'd flown the Concorde before, so he knew what to expect. But nothing prepared him for what happened that June afternoon as the Concorde roared down the runway.

BillLightfoot:  A piece of something shot vertically by my window, and that amazed me because the airplane was going over 200 miles an hour, I guess.  

Lightfoot loosened his seatbelt and peered through the tiny Concorde window. What he saw shocked him.

BillLightfoot: I could see there was a big, jagged hole actually in the wing of the airplane.

It was the size of a coffee table, he says -- about three feet by three.

BillLightfoot: Which by that time, had fluid coming out. Like, either fuel or hydraulic fluid, or something spewing out.

By now, the plane was accelerating quickly. Lightfoot buzzed for a cabin attendant.

BillLightfoot: I told her, "There's a hole in the wing. If you look here, you can see these a big, jagged hole in the wing." She says, "Everyone-- everyone thinks something's wrong 'cause it's the flaps." And I said, "No, no, no it's not the flaps.”

What happened next was nothing short of amazing. Lightfoot says the attendant walked away without even looking out the window.

BillLightfoot: I got her back, and I said, "You know, gee, I'm in the aviation business. I know airplanes and I need somebody to come look at it." Well, then she went up, forward to the cockpit. Video: How the Concorde disaster unfolded

He was becoming alarmed. How could the plane possibly make the journey from Washington to Paris? Then the cabin attendant returned.

BillLightfoot: She said, "I've talked to the pilot. We know what it is. We've blown a couple of tires, one or two tires. But it's not a big problem. We've blown tires before. And he knows about it (edit) but we're going to Paris, because our spare tires are in Paris.

Peter Greenberg: And you weren't buying that?

BillLightfoot: Well, no, because -- we got a bigger problem than that. We got a big hole in the wing. We got more than a tire problem.

By now the wing was shedding skin -- and gushing fuel and hydraulic fluid. (#41) then -- at long last -- a crew member appeared.

BillLightfoot: So I grabbed his head and just stuffed his head over by the window. So he could see it. And then he saw it and he said, "Mon Dieu."

After that, Lightfoot says, things started happening.

BillLightfoot: Just minutes later, you could feel the aircraft decelerating very dramatically. The pilot chopped the throttles and then started maneuvering.

First, the plane made a pass over Dulles for a visual inspection. The tower told the crew the two main rear tires had disintegrated. They later learned a piece of tire had taken a chunk out of the wing. Even so, the cockpit recorder shows, the flight crew wanted to head to Paris.

Only after another warning from the tower that the plane was trailing a vapor stream did the crew finally decide to return to Dulles. Catastrophe averted -- but only just.

Twenty-one years later, in the Paris suburb of Gonesse, 113 people were not as lucky, even though the Concorde had since been fitted with, among other things, stronger tires. But were they strong enough?

Bob Macintosh: There was a wake-up call. The wake-up call didn't solve the absolute problem of the big accident in Gonesse. But indeed, there was an industry effort to get the tire situation under control.

Peter Greenberg: Did they do it?

Bob Macintosh: Did they do it? If we look at the trend, the trend was decreasing. Did they eliminate it totally? No.

Others say they should have.

Greg Feith: When you look all the way back to 1979 and you look at all the events after '79, there was a systemic issue that should have been resolved. And I don't think it was.

So what did cause the crash of the Concorde? Was it, as French investigators say, largely the fault of that wear strip? Or was it caused, as some experts believe, by a chain of events? Soon it will be up to a courtroom to decide -- because in a highly unusual turn of events, Continental Airlines is now preparing to defend itself in a French court against manslaughter charges.

After the crash of air France Flight 4590 in July 2000, the Concorde didn't fly commercially for almost a year and a half. When it did return to the air, its tires had been redesigned and its fuel tanks -- reinforced. But its glory days were gone, its gas guzzling ways too costly. In 2003 the Concorde made its final flight.

But as we now know, the story wasn't over. Last summer, the French authorities accused Continental Airlines of a central role in the crash -- and charged it with manslaughter. Remember, it was a Continental Airlines DC-10 that French investigators said had dropped that metal wear strip as it took off minutes before the Concorde.

The prosecutor, echoing French investigators, accused continental of shoddy maintenance.  In their report, the investigators said the strip was "neither manufactured nor installed" properly.

Continental called the indictments outrageous and unjustified.

Carson Seeligson is an attorney -- and a legal consultant for continental.

CarsonSeeligson: We disagree that it was not properly installed. And we disagree that the wrong metal was used. And the FAA agrees with us. The work done by the technicians that day was reviewed by the FAA, which is our regulatory body.

Continental doesn't deny that the strip came off its plane -- but the airline does not acknowledge much else.

Peter Greenberg: So are you saying that continental has no accountability here?

CarsonSeeligson: We don't think that we were the cause of the Concorde accident that day.

Continental argues that planes often blow tires without crashing. So why, the airline asks, did a blown tire bring the Concorde down that day -- when it had survived tire problems so many times before?

CarsonSeeligson: There have been 57 other tire bursts on the Concorde in its history that this airplane recovered from. What was different about this day?

What was different? Continental -- along with some British and American experts -- argues it wasn't "just" that the plane was overweight, overfueled or delayed. Nor was it about a runway inspection that had been cancelled. A wind change. Or a spacer that was missing. It wasn't any "one" of those things -- it was all of them. Continental says the metal strip had a minimal role -- if it had one at all. And it adds there are eyewitnesses to prove it.

CarsonSeeligson: There will be -- we believe, evidence that something else happened before the tire burst.

Peter Greenberg: Meaning what?

CarsonSeeligson: Meaning that those who were watching the roll saw something happen to the engine, heard something happen to the engine before the tire burst.

Michael Chulkovs, a pilot for a U.S. airline, was preparing to fly his 767 to New York that day. He was one of those eyewitnesses.

MichaelChulkovs: I was located here by this green dot. And I was looking out at the runway. And I noticed the smoke come up from this area here by the blue dot.

Peter Greenberg: And the red dot?

MichaelChulkovs: The red dot is where the piece came off the continental.

That means, Chulkvos says, he saw the plane smoking before French investigators say it hit the wear strip. Other eyewitnesses have similar accounts. Remember the waiting 747 with the French president on board? Three years after the crash, the plane's pilot said "the fire began well before " French investigators said it did. And this: "I think the wear strip was an aggravating factor, but that something else happened preceding it.”

GregFeith: So who's to say that that piece of metal, that cut tire actually was the initiating event?

Former NTSB investigator Greg Feith -- who has worked as a consultant for continental on an unrelated case -- says these eyewitness accounts support continental's argument that contrary to what the French investigators concluded: the Concorde's missing spacer actually may have had an impact on the tires that day. 

GregFeith: Given the fact that we had a missing spacer, that could have caused a performance problem with the tires. That could have caused them to fail at any point during a high speed taxi or a high speed takeoff. Because those tires heat up because of the weight.

Mike Bannister: The former chief Concorde pilot for British Airways -- who may be asked to testify at the trial -- says we may never know the answer. If that missing spacer had not been missing, would that have had an impact? I believe that it would've had an impact. I just don't know how big it was.

As it conducted its own investigation into the Concorde crash from afar, without access to the evidence, Continental came up with its own version of what happened the day of the accident.

Continental says the Concorde started its takeoff role overloaded with fuel and extra bags. Within seconds, the tires on the left-side of the plane -- where the spacer was missing -- may have started to wobble because they were degraded. Eyewitnesses saw smoke and flames around the rear of the plane. After that, the tire hit that wear strip. Tire debris went flying and hit fuel tank five. Fuel gushed out and ignited. From the tower -- a warning. Video: Celebrities describe 'magnificent machine'

The Concorde veered left, toward the dirt -- hitting a runway light and setting the grass on fire.  The burning plane managed to get into the air. The crew fought to keep it up there -- but the plane couldn't get high enough fast enough.

Seconds later, it crashed.

So was the crash caused by a chain of events as continental claims? French investigators are sticking with their conclusion -- that the wear strip triggered the crash and once that plane caught fire, the crew couldn't save it.

Paul Louis Arslanian: Nothing could have helped them except turning off the fire.

PeterGreenberg: Which they couldn't do?

Paul Louis Arslanian: They could not.

French investigators ruled out the testimony of eyewitnesses saying it was unreliable. Documents show that 747 pilot for instance told two different stories about when he saw the plane catch fire. As for the spacer, they point to their test results and say it had absolutely no effect.

Air France has had little to say publicly about the crash beyond offering condolences and making settlements with relatives of the victims. The airline declined dateline's request for an interview. But questions remain about the role of the French airline.

Carson Seeligson: Why did this plane on that day fall out of the sky in 60 seconds? We think it's important that Air France be at the trial to explain that. And the fact that they won't be means that there will never be a real answer to what happened that day.

The pilots who flew the Concorde -- and loved it -- believe the skies are safer since the crash. Because even though the Concorde is no longer flying, other planes have benefited -- their electrical wiring is now better protected -- and their tires have been improved. 

Mike Bannister: So it has enhanced the-- the safety for all of us, from now forward, and into the future.

Lessons learned. And a hope sustained that maybe one day, elegance and grace will return to the skies -- and another white bird will beat time and sound -- to soar at the edge of space.

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