Four people, including two pilots, were killed in Indonesia Thursday when two military aircraft crashed into a mountainside during training, an air force spokesperson said.

Two Embraer Super Tucano planes took off from the East Java city of Malang on Thursday morning before losing contact half an hour later during regular formation training.

"All the bodies have been found," spokesperson Agung Sasongko Jati told AFP.

"Two are already in the hangar, two are still in transportation to the base."

He said the two pilots and two co-pilots were found after information from the public about where their planes had crashed. 

They were found on a mountainside near Mount Bromo in East Java, on Indonesia's most populous island, and the planes were believed to have hit a steep incline, Jati said.

Investigators are not likely to reach the site before Friday, when they will analyze the flight recorders and other data from the planes.

"The crash investigation personnel will come and know exactly what happened. They will have the voice communication, flight data, and the engine data and video," Jati said.

He told reporters the two turboprop light attack planes were in good condition.

Indonesia, a vast archipelago, has a poor air safety record despite relying heavily on air transport to connect its thousands of islands. 

It has suffered three major commercial plane crashes in the past nine years.