A United States Marine Corps F-35B Lightning II was damaged when a round fired from its own weapon pod exploded prematurely. The accident took place on March 12, 2021, at Marine Corps Air Station Yuma in Arizona, southwestern United States.
The F-35B was on a close air support training mission at night with an underbelly gun pod containing a 25mm GAU-22/A Gatling-type automatic cannon. The pod was specifically designed for the F-35B and F-35C variants that both lack an internal gun, unlike the F-35A.
The weapon fires 25mm PGU-32/U Semi-Armor Piercing, High Explosive Incendiary-Tracer (SAPHEI-T) ammunition. That type of round contains a fuse that triggers when it hit its target, setting off an explosive charge. It is unclear at this point if the fuse detonated untimely, or if the round was even fired intentionally.
Despite the damage, the aircraft managed to land safely. “The mishap did not result in any injury to personnel, and an investigation of the incident is currently taking place,” a Marine Corps spokesman told Military.com, who was first to report the event. The Naval Safety Center categorized the accident as a Class A mishap, which means the damage was estimated at more than $2,500,000 or the aircraft was destroyed.
While extremely rare, a fighter jet shooting itself is not unheard of. In April 2019, a Dutch F-16 shot itself with its 20mm rotary cannon during a training exercise over the Netherlands. In October 2018, a Belgian F-16 fighter was damaged beyond repair while parked at Florennes Air Base, Belgium, after a mechanic pulled the trigger of another F-16.
Update: The article was corrected. The original version wrongly said that the F-35 used APEX ammunition.