I've been on the other end of the curfew with non-compliant equipment, which is equally infuriating.

For a scheduled 6:00 a.m. departure, DL boarded the aircraft, pushed back, we taxied to the holding pen -- and then the captain came on the PA and announced that we would be sitting there 55 minutes until the 7:00 a.m. end of the curfew because DL had been forced to use a non-compliant a/c on the previous day.

So many things were wrong with how DL handled that one... but we were among the lucky ones as we had enough padding in the schedule to make our connection.