The crash killed 49 peopleeveryone on board except first officer James Polehinke, who was in critical condition Tuesday.
The jet stuggled to get airborne and crashed in a field after taking off Sunday from a 3,500-foot runway instead of an adjoining one that was twice as long. Experts said the plane needed at least 5,000 feet for takeoff.
The air traffic controller had an unobstructed view of the runways and had cleared the aircraft for takeoff from the longer runway, said National Transportation Safety Board member Debbie Hersman.
Then, "he turned his back to perform administrative duties," Hersman said. "At that point, he was doing a traffic count."
Earlier Tuesday, the Federal Aviation Administration acknowledged violating its owns policies when it assigned only one controller to the airport tower that morning. The policy is outlined in a 2005 directive requiring that control tower observations and radar approach operations be handled separately.
FAA spokeswoman Laura Brown said the controler had to do his own job keeping track of airplanes on the ground and in the air up to a few miles awayas well as radar duties.