A Bulgarian MiG-29 fighter jet crashed in a rural area during a routine training exercise on Thursday, the Novinite news agency reported.
The two pilots managed to eject safely before the jet plunged into a river near the southern Bulgarian city of Plovdiv.
The aircraft was participating in a joint Bulgaria-U.S. exercises, military officials said.
The cause of the crash is being investigated.
Eyewitnesses saw flames coming from the jet just before in went down.