MEXICO CITY — Mexican airline Aeromexico says it has fired three pilots involved in an accident that saw a jet crash belly-down into a field in July.

Investigators said earlier that a trainee pilot was improperly seated in the co-pilot's seat when the plane took off.

They said the plane's commanding officer took over controls from the trainee just before the crash.

The airline said in a letter to employees published Thursday that the pilots' actions were "in direct violation of our company's policies, manuals and procedures."

Investigators blamed a sudden downdraft known as a microburst for bringing the jet, and said there was no evidence of pilot error.

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