Google is your friend.
BA
http://www.britishairways.com/travel...y0_faq0_item11
What forms of ID do I need to check in at a conventional desk?
A Suitable forms of ID include:
Domestic travel
Credit card, Executive Club card, driving licence, company works card / ID.
Travel to the US
A Passport is required for all international travel.
Seems a bit strange, Executive Club Card as ID???????
However;
What to bring with you:
For international travel a passport and visa, where necessary, is required.
For travel wholly within the European Union a national identity card is also acceptable, where allowed.
When travelling wholly within the UK, there is no requirement from British Airways to carry any photographic identification.
When travelling it is strongly recommended that you carry a copy of your e-ticket receipt throughout your journey. Some destinations may require you to show it as proof of travel at Customs and Immigration.
If you have booked directly with British Airways, either through ba.com or a British Airways Telephone Sales office, and you paid with your debit/ credit card you must present that debit/ credit card at check-in. This is to assist the check-in process and to provide debit/ credit card verification.
When using a Self-Service Check-in kiosk, simply insert your credit card (for identification purposes only) to begin the check-in process.