American Airlines operates primarily out of Terminal 3 at London Heathrow Airport (LHR). This terminal serves as the hub for most of American's transatlantic flights and is also home to several of its oneworld® alliance partners, such as British Airways (select flights), Qantas, and Cathay Pacific. If you are a premium traveler, Terminal 3 offers some of the best lounge experiences at Heathrow, including the American Airlines Admirals Club and the prestigious Flagship® First Lounge. For those with oneworld Emerald status or flying in First Class, the British Airways Galleries First and the Cathay Pacific First Class lounges are also accessible and highly recommended. In 2026, American has streamlined its check-in process in Zone D of Terminal 3, utilizing enhanced biometric kiosks to speed up the bag-drop and security transition. It is always wise to double-check your boarding pass before heading to the airport, as very rare codeshare flights operated by British Airways may occasionally depart from Terminal 5.