MELISSA BLOCK, HOST:
Seven months after Malaysia Airlines flight 370 disappeared with 239 people on board, the search to find the wreckage has resumed. That search was on hold for several months while Australian authorities mapped the seafloor in the southern Indian Ocean, which includes some very rugged underwater mountain terrain. Now vessels outfitted with sonar and video cameras are back out on a mission that could take up to a year.
DAVID GALLO: It's like looking for two shoeboxes in the Rocky Mountains at night using a flashlight.
BLOCK: That's how oceanographer David Gallo of the Woods Hole Oceanographic Institute describes the task. He was a project manager for a similar search several years ago for the Air France jet that crashed in the Atlantic. Gallo says the hunt for the Malaysian airliner will proceed with what's called a sled - a sonar device lowered on a very long cable.
GALLO: So you can imagine a cable now that has to be three or four miles long worked back and forth across that terrain trying to pick up something that doesn't belong there. And the sound that bounces back forms a sort of an image of the undersea world. And today, those sonars can produce spectacular images.
BLOCK: How detailed would those images be?
GALLO: Well, we used them on Titanic. And you can see very small things. And you could pick up something as small as an ice bucket easily at about a half a mile's distance. So you can make very accurate maps of the seafloor. The trick would be though, in mountainous areas where there's landslides and things like that, just to pick out the bits of an aircraft against that kind of a background, which is not so easy.
BLOCK: They also, of course, need to know that they're searching in the right area. And that's been a huge problem through the months and months that this plane has been gone.
GALLO: I think that if there's one Achilles' heel about this whole thing is that is this the right haystack. You know, they've got a haystack now that's huge. And it's almost a ribbon of seafloor that extends hundreds of miles. And so, you know, the only way to know if they're right or not is to actually find the aircraft. It's a horrible situation to be in. So you've got to hope for the best - that the plane is found.
BLOCK: A key difference, I suppose, with the search that you were involved with for the Air France jet, you had floating debris. You found the plane ultimately. You found the black boxes. But you had stuff on the water, so you knew where you were headed.
GALLO: That was a great thing is that we knew that the plane had actually impacted the South Atlantic Ocean. In this case, there's no tangible evidence - not a pair of shoes, not a life vest, nothing to suggest that the plane is there except for the modeling. And that's why this is a very special and unusual situation.
BLOCK: When you talk to other people who have done these kinds of searches before, what are people saying? What are they puzzling over in this case?
GALLO: You know, it's very interesting to me that even in quiet conversations behind closed doors, it almost always ends with the statement so what do you think really happened - like a whisper. It concerns me because there's a certain doubt about whether the plane might actually be somewhere off the west coast of Australia. And, you know, at this stage of the game, we've got to put our confidence in that team and in those calculations.
BLOCK: It sounds like you are pretty certain that they will find this plane or be certain that it's not in this area.
GALLO: You know, it's a tough - that's a tough question. We were in the situation where we were - a year after the Air France 447 tragedy, we had our first expedition. And we spent two months looking and came back with nothing.
And I can tell you, it's an incredibly horrible feeling because you have the pressures of the family - that you feel like you've let the families down. And then the public pressure starts building.
Did you miss it? That goes through your own mind. You know, did we actually miss the aircraft. And you start to replay every bit of that expedition and look at all the data again and again and again. And unfortunately, the only way to get a conclusive answer is to find the aircraft.
BLOCK: That's David Gallo. He's an oceanographer at the Woods Hole Oceanographic Institute. He was a U.S. project leader in the search for Air France flight 447 in the Atlantic. Thanks so much for talking with us.
GALLO: You're welcome, Melissa. Transcript provided by NPR, Copyright NPR.