Controller Aircraft (CA), originally Controller of Aircraft, is a senior (3 star) British Ministry of Defence appointment who is responsible for delivering an airworthy aircraft to the Services, whereupon the Service issues a Release to Service (RTS), releasing the aircraft into service. The difference between CA Release and RTS is normally one of Build Standard. Although usually held by a Royal Air Force officer, several civil servants have held the post in the 20th century. The incumbent is a member of the Air Force Board.