Two Pakistan Air Force (PAF) pilots were killed Tuesday when their Mirage trainer aircraft crashed after exploding in mid-air, a media report said.The crash took place in Baldia town near Karachi and injured many on the ground, Dawn online reported.Eyewitnesses said that the plane exploded mid-air.Three buses caught fire as the aircraft's debris spread far and wide and a number of nearby buildings were damaged.The crash reportedly took place due to a technical failure.