It was the biggest mystery of 2014, and investigators are hoping the new year will bring fresh answers about the fate of Malaysia Airlines Flight 370.
Nine months after it disappeared from the sky with 239 people on board, there has been so sign of the Boeing 777 in the Southern Indian Ocean.
"Where's the floating debris?" asks Capt. John Cox, NBC News aviation analyst. "I've expected for months that we would find light objects — things like Styrofoam cups or flotation cushions or other light particles from the airplane."
An underwater hunt that has already trawled more than 4,000 square miles of the ocean floor hasn't yielded any clues. That effort is expected to wrap up in May, at which point the countries involved will have to decide whether to keep searching — and where.
"That's a big ocean there, the Indian Ocean down there is really big and treacherous," said Steve Chealander, a former National Transportation Safety Board member. "It's really hard to cover all of that and try to find out where it is. "
The search area is based on pings between the plane and satellite before it went missing on March 8 while flying from Kuala Lumpur to Beijing.
"It could be an effort like the Titanic, where it could be years, not months."
The radar and satellite evidence suggest someone turned the plane around and disabled its transponders. One theory is that everyone on the aircraft was somehow incapacitated and the plane just kept going until it ran out of fuel and crashed.
But the absence of any sign of the plane has some questioning even that scenario.
"The reality is that we really do not have any proof at all of what happened to this airplane," said Sarah Bajc, the girlfriend of Phillip Wood, a Texas man who was on the plane.
"We don't have proof that it crashed in the water at all. There's been not a trace — not a tiny, tiny bit of evidence that it's crashed in the water."
Greg Feith, a former investigator for the NTSB, said he believes the plane can still be found, but there's no guarantee it will happen in 2015.
"It could be an effort like the Titanic, where it could be years, not months," he said.