Three planes fatally out of balance force investigators to question every calculation. It's a flight risk that's entirely preventable, and yet repeated disasters reconfirm the need for critical backup systems. With nearly 90,000 pounds of denim on board, a cargo plane in Miami crashes moments after lifting off. A packed commuter flight slams into a North Carolina hangar, revealing a deadly industry oversight. And, the NTSB is called in when a jumbo jet loaded with armored military vehicles pancakes to the ground in Afghanistan.