The cookie policy addresses this directly ...
Originally Posted by ba.com
Use of cookies by British Airways
Cookies are small text files that are placed on your computer by websites that you visit or certain emails you open. They are widely used in order to make websites work, as well as to provide business and marketing information to the owners of the site.
British Airways uses cookies on ba.com for the following purposes:
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Ease of use
Cookies are used to enhance the ease of use of ba.com for customers. For example, to:
remember customers’ country of choice and presenting relevant content.
keep track of customers’ Executive Club number when they have logged in.
remember the selected departure airport when booking a flight.
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Cookies are sent back to the site that created them, regardless of multiple tabs.
And no, I've never read this before either. I just blithely click on the 'ok' button
hth