Heathrow Terminal 4, opened in 1986, is amongst the few stations on the London Underground to have a single platform, and is the only one with a one-way train service.

Trains to Terminal 4 run in a clockwise direction around the one way loop from Hatton Cross (westbound) to Hatton Cross (eastbound) via Heathrow Terminal 4 and Heathrow T123. Trains usually wait for a few minutes at Heathrow Terminal 4 station, as this serves as the terminus of the line.