Our flight to Barcelona was fine, but the return flight was a nightmare. When we arrived at the airport at 6am and got in the AA line, the AA rep informed us that the flight was cancelled and we would be put up in a hotel for the night and rescheduled for the next day. We found out the reason for the cancellation was that they had an expired safety certificate for that plane and it had been grounded until the problem was fixed. This resulted in about 50 people that day and 150 people the previous day being stuck, missing work and connections to other flights. They told us to meet them at 9:30 and we would be bused to a hotel. It wasn't until 11:45 that they got us on a bus. They had a bus at 10:00 that wouldn't hold all of us. The AA rep designated which people to get on the bus, but many people who were to wait for the second bus forced their way around us and took our places. They didn't let us know until about 9pm that night what the arrangements for the next day would be. Fortunately, we were able to get to Miami and then home although very late the next night.