Around 10% of American commercial airline pilots are allowed to bring an extra tool to work.
A Federal Flight Deck Officer (FFDO) is a Part 121 Airline Pilot trained and licensed to carry a firearm to help defend commercial aircraft against hijackers. A Part 121 Pilot flies an aircraft requiring two cockpit pilots working with a flight dispatcher. Overseen by the Federal Air Marshal Service, a law enforcement agency under the Transportation Security Administration's (TSA) supervision, Air Marshalls travel incognito on commercial flights to help protect against terrorism.