Two Italian Tornado fighter jets collided in mid-air during a training exercise on Tuesday.
Four crew members are missing after the military planes hit each other and plunged into a hillside, causing a forest fire.
It happened on the east coast of central Italy, some 30 kilometres from the town of Ascoli Piceno in the Marche region.
It is believed the crew members ejected before impact but there is no word on their whereabouts.
There were no civilian casualties and the fire is now said to be under control.