Not on a flight, but at a hotel. Our family name is extremely rare. About fifteen years ago, brother-in-law and his wife (who live in Canada) asked my husband and me to come to Atlanta where BIL would be performing in a concert (he is a classical musician). We were all staying at the same hotel, two different hotel rooms (obviously). They arrived first, checked in, no problem. We arrived and were told we had no reservation. Impossible. We gave them our name. Our reservation number. The CC under which it was booked. Nothing. It was the middle of the night. We asked to speak to a manager. They said they would call the manager. An hour passed. It seemed they meant they would call the manager in the morning. At that point we realized (meaning I realized) we would have to find another hotel if we were going to salvage the weekend. The next day, after we called a couple times, we got a call back from the manager of the first hotel. He explained that when BIL and SIL checked in, "the system" automatically cancelled our reservation. We figured the FD clerk was the one that did the cancelling, on grounds that it was an extremely rare last name and therefore it must have been an erroneous double booking. When we showed up, no one wanted to confess to the mistake.