In February on a 744 return from CPT, the old girl went tech (an engine sensor that had become senseless) and we were delayed for 25 hours. That cost them a very considerable amount of hotac and €600 euros per pax.There were some 300+ pax on that flight - we were already boarded and doors closed. Then 90 mins delay as problem only found at start up. Then canx. BA paid up promptly but that is well over £160,000 in one hit before Hotac and crew costs. I know they have insurance against these things but that was a heavy price to pay for the old lady.
Incidentally, it made me wonder how many that voted for Brexit also voted to leave EU.261