Pilot error was also being considered by accident investigators yesterday. It is possible the slats in the leading edge of the wing or the flaps at the rear edge were not in the right position to give the aircraft the proper degree of lift. The cargo may also have shifted just after take- off or may have been unevenly distributed. It is understood, however, that the plane was not heavily laden and that disastrous engine problems were a more likely cause.
Two of the four Pratt & Whitney JT9D engines on the aircraft could have failed, which would explain why air traffic controllers believe the aircraft only managed a height of 300 feet before it fell. It came to rest just a mile from the runway.
If only one engine was out of commission, the pilot should have been able to take off safely. It is possible, however, that one engine began to disintegrate and that parts of it struck the other engine on the same wing.
Part of a 10-strong team from the air accident investigation branch of the Department ofTransport examined the south-western edge of the airport yesterday for wreckage from the engine, which they hope to reassemble.
Air traffic controllers had received no mayday message. "As far as we are concerned, the plane took off normally. The next thing we knew it had crashed," said an air traffic control source.
Investigators have found the "black box" located in the cockpit, which should contain recordings of any conversation in the flight deck immediately before the plane went down. Last night the other black box, which records the movement of the aircraft, had not been found.
Investigators are confident that they will be able to isolate the cause of the crash relatively quickly and said an interim report will be available early in the new year.
Kieran Daly, the editor of Air Transport Intelligence, an Internet news service, said that one obvious line of inquiry was the performance of the engines, another that pilot error meant the plane did not have sufficient lift. "What seems obvious is the aircraft became rapidly uncontrollable and barely cleared the perimeter fence," he said.