Two light attack aircraft crashed in Indonesia's East Java province on Thursday, killing all four people aboard, according to the Indonesian Air Force.

The two Super Tucano turboprops with tail numbers TT-3103 and TT-3111 hit a steep slope of Mount Bromo volcano while conducting a routine flight-formation exercise in Pasuruan district, said First Marshall Agung Sasongkojati, spokesperson of the Indonesian Air Force.

The incident left two pilots and two other crew members dead, according to Sasongkojati.