The Air Force says an F-16 fighter jet that went down near Luke Air Force Base in suburban Phoenix most likely hit a bird.

Two pilots who were practicing landings and takeoffs at the base Wednesday evening ejected safely and the fighter crashed in a farm field near the base.

Base spokeswoman Lt. Candice Dillitte said Thursday that there's nothing to indicate a fleet-wide problem with the jets. The Air Force operates more than 1,000 of the single-engine fighters.

The base 15 miles west of Phoenix in Glendale, Ariz., trains pilots and has more than 130 F-16s.

Witnesses say the plane's engine was popping after it took off from the base and they watched as the pilots ejected.

Bird strikes can severely damage jet engines.