Cargo jets currently don't have fire suppression ability inside the containers carrying the cargo-- with the exception of the dangerous goods container.
My guess is the fire was simmering in the cargo hold inside a container at high altitude, then flamed up in the descent to Memphis as the aircraft pressurized closer to sea level (more oxygen).
MEMPHIS, Tenn. - A FedEx cargo jet caught fire and veered off the runway while landing at the Memphis airport Thursday. One minor injury was reported.
No cause had been determined, but a preliminary investigation indicated the plane's right landing gear collapsed before the fire began.
"It would appear that would be the sequence," said Ted Lopatkiewicz of the National Transportation Safety Board (news - web sites), which sent a team to Memphis.
The MD-10, a widebody cargo jet, was arriving on a flight from Oakland, Calif., when the accident happened. The flames were extinguished but the plane was heavily damaged. Several large holes burned in the right side of the fuselage, which was blackened by smoke.
Two crew members and five employees on board exited the aircraft safely through windows, officials said. One suffered minor injuries in the evacuation.
FedEx spokesman Ed Coleman said there was no indication from the crew of an emergency before the landing.
FedEx often transports hazardous materials, but company spokesman Jim McCluskey said officials were still determining what cargo was aboard the aircraft and whether it was damaged.
"There's no evidence whatsoever of a bomb or any terror activity," he added.
The jet "landed and veered off the runway," said Kathleen Bergen of the Federal Aviation Administration (news - web sites). Television images showed the plane's right wing on the ground.
The Memphis Fire Department said six firefighting units were dispatched to the airport.
Memphis-based FedEx owns the world's largest cargo airline. Thursday's incident was the fourth involving a FexEd jet in the last seven years.