In any case, by 8 p.m., when the departure approached, Calombaris went back to the hotel without changing the tires. He left Philippe behind to fly on with the plane to Sokoto, where Philippe again intended to change the tires. The spare wheels were still inside the plane.

But the plane stayed on the tarmac in Jedda for about 12 more hours before it took off.

Nationair president Robert Obadia blamed the delay on the airline's broker, AGOS America Ltd. AGOS had arranged to lease the plance for hajj duty to a Nigerian client, Holdtrade. AGOS asked that Nationair not leave Jedda until it had received advance cash payment from Holdtrade, Obadia said.

The cash issue was settled, Obadia said, and the next morning, July 11, the 247 Nigerian passengers boarded the airplane.

It was already a sweltering 30 degrees Celsius when at 8:29 a.m. the 23-year-old DC-8 started lumbering down the Jedda runway with a full load of passengers and baggage and four spare wheels in the hold. Co-pilot Davidge was executing the takeoff.

After travelling a short distance down the hot tarmac, a tire on the left side of the plane suddenly exploded and ignited, crash investigators have found.

Large fragments of the tire peeled off the wheel and tumbled across the runway. Then the second tire on the left side blew.

At that point, voice recordings reveal co-pilot Davidge telling Allan, his captain, that they had a blown tire, Barayan said.

It was still early in the takeoff roll. Skid marks and tire and wheel debris show the plane was only about 150 meters along a 4,000 metre runway and had barely gained speed. The blown tires would clearly have affected the plane's progress, Barayan said.

Nationair policy, like that of most commercial airlines, leaves the decision to abort a takeoff strictly to the pilot. Yet Allan did not order the co-pilot to abort the takeoff. Why not?

The question may never be answered.

Allan simply ignored his co-pilot's statement, Barayan said. "It's a pure judgement thing and he's paid for it,"Barayan said.

The image of a co-pilot trying to control a plane of takeoff with two blown tires and waiting for orders that never came raises serious questions for the investigators.

"Some people would say if the co-pilot is doing the takeoff he should have the responsibility to reject (abort) if he feels he'd like to reject," Barayan said. "Other people say, no, this should be the pilot-in-command's responsibility and should not be taken away from him. So this one issue is going to raise a big controversy in the industry."

Unlike newer planes, the DC-8 had no heat sensors in the wheels that would have alerted the crew to the fire. So, as the plane rose into a clear sky, Davidge, unaware of the danger, raised the burning landing gear into the aircraft's belly.

The fire quickly spread through the interior. As the plane reached an altitude of 900 metres, a third tire exploded inside the wheel well, and together with the fire, knocked out the plane's electrical and hydraulic control systems.