Federal Flight Deck Officer
A Federal Flight Deck Officer (FFDO) is an airline pilot who is trained and licensed to carry weapons and defend commercial aircraft against criminal activity and terrorism. The Federal Flight Deck Officer program is run by the Federal Air Marshal Service, and an officer's jurisdiction is the flight deck or cabin of a commercial airliner or a cargo aircraft while on duty.
Source: Wikipedia — Federal Flight Deck Officer (CC BY-SA 4.0)