Passengers suffering cancellations and delays may be entitled to compensation, but the issue is not clear despite European regulations.
ABTA said its legal department believes customers have a strong case. But compensation will depend on whether BA can demonstrate it did everything possible to prevent problems.
The Air Transport Users Council, which handles passenger complaints, reported few people had been in contact. It had no calls about Terminal 5 in the first two days of this week, although things may change.
AUC chief executive Simon Evans said: “BA could be handling this better than it has been given credit for. Big news stories frequently do not trigger the number of complaints you might expect.”
A BA spokeswoman said: “We are offering passengers hotels, food and drink, and transfers in accordance with the regulations. We gave vouchers for hotels on the first day. But we have said people can claim all reasonable costs