It’s a big call to “cancel” a flight for engineering reasons as it’s an extravagant cost to shuffle PAX off to hotels and the like
Back in 2018, we were boarded the QF127 A330 for SYD>HKG for a 9:30am departure.
Everyone on-board all doors closed, all equipment has moved away from the plane.
~9:30am Pilot announces small delay due to technical issue, once engineers sign off we'll commence.
~10:00am push back, taxi to runway. Hold for about 10mins. Pilot announces tech issue, need to return to gate.
~11:00am Still working on Issue, awaiting engineering sign off, should be departing soon
~12:00am push back again
~12:30pm holding on taxiway this time, pilot announces return to gate
~1:30pm Pilot announces major issue flight unlikely to leave. Awaiting arrival of another A330 later that afternoon to operate QF127
(another reason not to rush into PJ's folks!)
I was in Economy, there was a lady across the aisle who frustrated but wasn't venting. I invited her up to the lounge to wait it out.
Finally about 6pm we departed, on a completely different A330, but all in the same assigned seats, except for a few who didn't come back.. This was at the time we should've been arriving into HKG. And of course by the time we did arrive into HK, the airport was dead quiet, the HK Airport express had stopped running.. It was a long day.