Investigators say it only took a moment: The lone traffic controller at Blue Grass Airport cleared a flight for takeoff, then turned his back to handle administrative work.
What the controller didn't see, a federal investigator said, was the Atlanta-bound jet heading down the wrong runway.
Moments later, Comair Flight 5191 struggled to get airborne on the shorter runway and crashed in a nearby field. The crash killed 49 people - everyone on board except first officer James Polehinke, who was in critical condition.
Separately, the Federal Aviation Administration acknowledged violating its own policies when it assigned only one controller to the Lexington tower. The two developments began to explain factors that may have contributed to Sunday's crash, the nation's worst airline disaster since 2001.
On Wednesday, families of the victims were scheduled to tour the crash site before a memorial service. Three days later, pieces of doomed airplane are scattered, the field is stained with engine fuel and trees by the runway have both bright green leaves and charred black ones. The few personal items gathered at the site are covered with transluscent plastic.
Authorities said the pilot tried to take off from a 3,500 foot runway instead of an adjoining one that was twice as long. The air traffic controller, a 17-year veteran at the airport who has not been publicly identified, had an unobstructed view of the runways and had cleared the aircraft for takeoff from the longer runway, National Transportation Safety Board member Debbie Hersman said.
Then, "he turned his back to perform administrative duties," Hersman said. "At that point, he was doing a traffic count."
The FAA admitted it violated a policy, outlined in a November 2005 directive, requiring that control tower observations and radar approach operations be handled by separate controllers.
FAA spokeswoman Laura Brown said the controller at the Lexington airport had to do his own job - keeping track of airplanes on the ground and in the air up to a few miles away - as well as radar duties.
Polehinke was flying the plane when it crashed, but it was the flight's captain, Jeffrey Clay, who taxied the aircraft onto the wrong runway, Hersman said. Clay then turned over the controls to Polehinke for takeoff, the investigator said.
The plane hit a fence and trees and crashed in a nearby field.
Polehinke was pulled from the burning plane after the crash but has not been able to tell investigators why the pilots tried to take off from the wrong runway. Before Hersman's briefing on Tuesday, the NTSB said Polehinke was flying the plane; it made no mention of Clay being the one who taxied the plane into position.
Both crew members were familiar with the Lexington airport, according to Hersman. She said Clay had been there six times in the past two years, and Polehinke had been there 10 times in the past two years - but neither had been to the airport since a taxiway repaving project just a week earlier that had altered the taxiway route.
Federal officials are looking into whether runway lights or a repaving project a week before the crash confused the crew into turning onto the wrong runway.
Polehinke had a clean record as a pilot, with no accidents or mistakes, authorities said. He spent five years - from 1997 to 2002 - flying short-range, twin-engine planes for Florida-based Gulfstream International Airlines. He flew at small airports all over Florida and the Bahamas, starting as a first officer and getting promoted to captain in 2000.
The FAA acknowledged violating its own policies when it assigned only one controller to the Lexington tower.
It was unclear Monday just when the pilots might have realized they were on a runway too short for their plane.