AA delayed my flight out of LHR once by just under a day. No compensation beside food vouchers and put up in a hotel. EU rules applied to them since it was a flight operating into/out of the EU at the time. Reason for delay? Staff shortage due to a (false) fire alarm at their local crew rest hotel meaning the crew could not operate the flight.

They claimed such an incident was outside their control and unforeseen. Yet it happened several times in the year odd before my flight. I would have thought they have substitute crews on standby (maybe from an alliance pool?), and at the very least not put all their crew in 1-2 hotels.

They told me fire alarms were unusual. I sent them a UK gov report showing hotel fire alarms happened hundreds of times in the prior year. No change. I no longer fly AA- but I don’t expect any US carrier to act differently. Sadly.