TOKYO — Wind shear may have caused the crash of a FedEx jet that cartwheeled on the runway at Tokyo's main international airport and burst into flames, investigators said yesterday, but experts said that the model was notoriously difficult to land.

The American pilot and co-pilot — the only two people on board — were killed when the MD-11 cargo plane bounced on its landing at Tokyo's Narita international airport, slammed onto the runway and tipped onto its side before exploding into flames.

Kazuhito Tanakajima, an aviation safety official at the Transport Ministry, said the crash may have been the result of wind shear — sudden changes in wind that can lift or smash an aircraft into the ground during landing.

Planes can lose airspeed suddenly and/or lift abruptly if a headwind suddenly changes to a tail wind during takeoff or landing, said Patrick Smith, a Boston-based aviation analyst.

Tanakajima said there was headwind of about 45 miles per hour.

Smith said a 45 mph headwind would be unusually powerful.

"It is possible that shears from these gusts, together with known instability issues of the MD-11, led to the accident," Smith said.

Tomoki Kuwano, a former Japan Airlines pilot and aviation expert, said the MD-11 has a record of landing failure and "often flips over" when that happens.