A helicopter deck (or helo deck) is a helicopter pad on the deck of a ship, usually located on the stern and always clear of obstacles that would prove hazardous to a helicopter landing. In the United States Navy, it is commonly and properly referred to as the flight deck. In the UK's Fleet Air Arm, landing on is usually achieved by first lining up on the port quarter parallel to the ship's heading, then once the deck motion is deemed to be acceptable the pilot sidesteps the aircraft laterally using a white painted line (the bum line) as a reference.