Latest information about Heathrow Terminal 5, which is exclusive to British Airways:
www.ba.com

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    Access by London Underground (Piccadilly line)

• Train frequency: every 10 minutes or so (or more frequent at peak times).
• When boarding a westbound Piccadilly Line train to Heathrow, be sure to get the train to "Terminals 123 and 5", not one to Terminal 4 (around the loop and back to Central London via Terminal 123).
• Heathrow airport is in fare zone 6.
• On arrival, take the excalators and lifts from the platform level to Ground level of the Terminal.