MEXICO CITY — Mexican investigators say a sudden downdraft known as a microburst was apparently responsible for bringing down an Aeromexico jet that crashed belly-down into a field in July.

The Transportation department said there was no evidence of pilot error, but acknowledged a trainee was improperly seated in the co-pilot's seat when the plane took off. It said the plane's commanding officer took over controls from the trainee just before the crash.

All 103 people aboard survived, some with injuries, in the July 31 crash.

A U.S. passenger has filed suit against the airline, saying Aeromexico was negligent in improperly taking off during a severe storm.

The department said Wednesday "there was no information that would have made the crew consider delaying takeoff."

Many Mexican airports don't have wind shear alert systems.