Originally Posted by
KenJohn
Two aspects.
BA and IB are one company; i.e. IAG. If BA and/or IB went under, there will be no ability to spend Avios wherever you left them.
Not picking up on the OP's original question, but the response above is inaccurate - BA and IB are seperate legal entities. It is entirely possible for one to go out of business and the other to continue trading.
Probably less likely to happen in practice, and I am sure there would be a trade buyer for the subsidiaries' assets, operating licences etc. But certainly these two principal operating subsidiaries are not intertwined for that purpose.