If a flight is cancelled, airlines must get customers to their destination as quickly as possible at no extra cost, even if it is with a rival carrier.
Alternatively, passengers can take a refund, which should also be offered for flight delays of more than five hours.
In Catie and Phil's case, the alternative flight offered would not have arrived until Saturday morning - four days into their week-long holiday.
So they took the refund. That was not easy. The chatbot only seemed to allow them to rebook, and it took more than an hour waiting to speak to BA on the phone before the refund was confirmed. It will take a week to be paid.
When airlines are at fault, extra compensation is paid under UK and EU rules. But not this time, because the air traffic control issues were beyond airlines' control. Even so, airlines themselves are furious that they have been saddled with a bill of millions of pounds.
BA also refunded the couple's car hire, which had been organised through the airline. The problem for the couple was that they had booked accommodation and excursions separately, and that is money they have lost.