15-year-old airliner rips open mid-flight

>>> very close call . 34,000 feet over the skies of arizona last evening. when a large hole ripped open atop a souwest alines jet full of passengers. the oxygen mask we hear about on those routine preflight safety announcements became life safers to passengers. the interior of the plane was exposed to open daylight. dozens of the airline's 737s are grounded, temporarily taken out of service by southwest itself. and invest gators are racing to learn what happened and whether there may be a larger maintenance problem with the fleet. tom costello is in our washington bureau now with more.

>> reporter: lester, nearly 80 southwest 737s have been taken out of service as southwest looks for any signs of the kind of cracking that may have caused this hole to open up midnight. 118 passengers on board along with five crew members. they all got off alive, one flight attendant and a few passengers passed out from a lack of oxygen as air was sucked out of the cabin. investigators on the ground in yuma, arizona today looking over the southwest 737 that made an emergency landing late friday, after a five-foot hole ripped off midnight. passengers described a loud bang, then a rush of heiress caping from the cabin.

>> and bam, i mean, just incredible noise, and then while you're trying to process what just happened, then oxygen masks come down.

>> not everyone was getting their mask on. some were having problems, people were passing out. it was not good.

>> reporter: flight 812 had just approached flying altitude, when a large portion of the skin rip ripped open, right over the passengers heads. the pilot quickly descended then made an emergency landing at a military base in yuma.

>> i thought we were going down, i really did.

>> any time you have a rapid decompression of an aircraft is a big deal , just from the standpoint of safety. it is a startling event not only for the passengers, but the flight crew .

>> reporter: the plane involved, a 15-year-old 737 300. another southwest plane had a hole open up in the roof nearly two years ago, forcing an emergency landing in west virginia . airlines were ordered to inspect 737s for signs of metal fatigue . two years ago, the faa find southwest $7.5 million for failing to conduct timely crack inspections on its 737 fleet. we talked to the ntsb on the scene.

>> we will be looking at everything. right now we are here to look at this accident, and if we find issues related to this accident that could be applied to the rest of the fleet, we will make that point known.

>> reporter: and metal fatigue has led to tragedy. in 2005 , a chalk's airways plane crashed on takeoff from miami when its wing ripped off. in 1988 the top of an aloha airlines plane tore off in flight. a flight attendant was sucked out of the plane to her death. metal fatigue is caused by the constant movement of an airplane, the constant contraction and expansion. this aircraft was 15 years old, with nearly 40,000 cycles.

>> as you know, there are an awful lot of 737s in the sky, a lot of them doing a lot of short hops, takeoffs and landings as you described. what's the word on the airplane right now.

>> this is a workhorse for the industry, as you well know, but it is aging. southwest has been trying to remove or get rid of the 737 737 300s and replace them. the faa says in the united states right now, there are a total of about 288 737-300s in service worldwide, about 1,000.

>> tom costello in washington, thank you.

>>> greg fife is a former ntsb investigator, he joins us from denver. i think a lot of people are looking at this, a three-foot hole in an airplane, how much danger were these passengers in? could this plane have crashed?

>> no, not from the standpoint of this type of failure in the fuselage itself. the big thing is, if there was a structural compromise where -- like aloha where you lost a very big chunk of that airplane. in this case it ripped off a three to four foot hole. there's tear straps under the skin to prevent that rip from propagating even further. from that standpoint they were never in danger of crashing this airplane.

>> we have seen these incidents before. has the industry underestimated the toll that age and repeated landings and takeoffs take on airplanes?

>> i don't think they've underestimated it, lester, i think we have to be very cautious, because we know from history, there's been aging aircraft issues and, of course, this is an older aircraft. we have to look at the fact that this is a new event the. it could be something totally unrelated to the process of aging aircraft, but more to the inspection now. there are comprehensive inexpectations and they could induce damage, the mechanics could induce damage by doing some of these inspections. we have to wait until the ntsb does its investigation.

>> at 34,000 feet, you have to get oxygen on in a hurry or as we saw on that flight, people start passing out.

>> i think security now is more highlighted than safety with regard to -- these are rare events as far as a rapid decompression or explosive decompression . i think from the standpoint of security, they're more concerned about the bad guys doing something bad in a laboratory, with an oxygen generator as we've seen, the damage that can be done from valujet. i think if there is an event like this, whoever is in a lavatory at the time, will have to find their way to an oxygen mask . i think the odds are against somebody being compromised as far as their health is concerned without a lavatory oxygen generator .

>> thanks for sharing your expertise