The officer in command of, and typically having ultimate authority over, a military unit.
The executive officer, second in command of a naval vessel.
Air Transport Auxiliary rank corresponding to Flight Lieutenant in the Royal Air Force.
Women's Royal Naval Service rank corresponding to Lieutenant-Commander in the Royal Navy.
The copilot of an aircraft.
The chief mate of a merchant ship.
The most senior civil servant in the United States Foreign Service, with responsibility for running an embassy under the authority of and reporting to the ambassador.