All customers with a cancelled flight are entitled to another flight and could also be entitled to compensation.
Passengers are due compensation if the cancellation was announced less than two weeks in advance and the airline was responsible.
Which? Travel has called for the Civil Aviation Authority to investigate British Airways over recent cancellations.
Rory Boland, editor of Which? Travel, said: “Our investigation found British Airways neglected to tell passengers about their right to compensation and left families significantly out of pocket by failing to reroute them.