Two training aircraft belonging to the Pakistan Air Force collided in midair Thursday, killing two pilots and two co-pilots, dpa quoted military and police officials as sayinig. Wreckage fell onto a compound, injuring nine civilians, police official Ishaq Khan said by telephone. The crash occurred over Rashakai town near the Nowshera district of the north-western province of Khyber-Pakhtunkhwa while the two Pakistan-made Mushaq training planes were on routine training flights. Khan said the pilots and co-pilots of both planes were killed. Wing Commander Mashkor Hussain confirmed the aircraft crashed but said the cause of the collision was so far unclear. Crashes of two-seater Mashaqs are common in Pakistan. In December, two pilots were killed when a trainer plane crashed in the south-western province of Baluchistan.