The Air Force says an error by the backseat pilot is what caused parts of a KA-1 aircraft to detach midflight and fall on Pyeongchang County, Gangwon Province, during a nighttime live-fire drill on Friday.

According to the Air Force on Monday, the backseat pilot pressed the emergency jettison button after mistaking it for the heater control switch, causing two gun pods and two empty fuel tanks to fall from the aircraft. 

The Air Force said the pilots were wearing night vision goggles over their visors and the backseat pilot pressed the emergency jettison button by mistake while trying to adjust the vent outlet, unable to see due to the hot air from the vent. 

An Air Force official said the emergency button and the heater control switch are similar in size, and that both are round and need to be pressed. 

The Air Force will decide what disciplinary action to pursue after a meeting of its disciplinary committee.