ACOSTA: We are following investigation into the fiery crash of a plane in Afghanistan that killed seven Americans. The stunning video of the plane falling from the sky has gone viral, may provide some clues. CNN pentagon correspondent, Chris Lawrence, has the latest.</s>CHRIS LAWRENCE, CNN PENTAGON CORRESPONDENT (voice-over): There were thunderstorms in the area when the Boeing 747 reportedly shown here stalled and crashed in Afghanistan. So, whether it is one potential cause, weight is another.</s>STEVEN WALLACE, FORMER FAA OFFICIAL: The overall weight has to be within center of gravity limits. If cargo shifts in either direction, it is possible it could go out of the limits.</s>LAWRENCE: So, it is not just the total, but where that weight was positioned on the plane. As part of the draw down in Afghanistan, the U.S. has been removing a massive amount of heavy equipment. So this 747 takes off for Dubai with five armored vehicles on board. Each weighing 13 tons and has to be locked in a certain spot. But, if one of the chain attachments were to fail, one loose vehicle could push 20, 30 tons to the rear of the plane. A lot of people at home wonder, what's the difference between this flight and a 747 they might get on?</s>WALLACE: Well, This is a 747 400. It is a very widely used commercial passenger airplane with an excellent safety record.</s>LAWRENCE: And whether you are playing tourist to Australia or holy gear from Afghanistan, balance is essential. Even carrying the space shuttle discovery on its back, this 747 weighs less than 500,000 pounds. Compare that to the same plane with hundreds of seats, passengers, luggage and food, it can weigh 800,000 pounds. The airlines are so precise, they add five pounds to the average passenger's weight in winter to account for heavier coats and boots. Chris Lawrence, CNN, Washington.</s>ACOSTA: Coming up, inside the mind of a killer. Could biology explain the motive for the Boston marathon bombers? Our doctor Sanjay Gupta is investigating.
Seven Americans Killed In Plane Crash In Afghanistan