This is my concern. My two are pretty lousy at waking to standard alarm clocks anyway which doesn't give me huge confidence.
We recently had an alarm go off in the early hours. Fortunately it was only the CO monitor announcing its own expiry and intention to never work again (re-ordered ASAP) but despite its shrill caterwauling, neither DC nor DH were roused. If that wasn't a false alarm the consquences could be devestating. I can't do much about DH, but the optics of child not rousing and being left unattended are a hell of a lot worse than the whole household failing to wake. Objectively whole household is worse, but if the guilt and social stigma can be avoided, that's a worthy option.
If the DCs were woken it would be concerning to them. We've had power blips before and I've seen DS(14) go to the fuse box, and they're briefed on the stopcock (to much sniggering... and ballcocks in the toilet was more than their adolescent humour could take
) But there is a key difference in launching into problem solving mode when fully concious to having been woken abruptly. There's also the added difficulty of getting external support to help.
My boundaries are lighter than MN average. DS1 was happy with a couple of hours alone from 10. DS2 was walking a short distance home, letting himself in and alone for 10-15 mins from 9, but took longer to build up to a couple of hours. At 12/14 I'm happy to leave them for several hours within waking hours, but my boundary is that they need to be awake. This winter will be the first babysitter-free Christmas parties because they'll happily be awake in the time we'll be out and happy with that time span. In the mornings on school holiday, I prefer to wait until one is awake before I leave the house so one of them is alert and knows what is going on.
I wouldn't leave a 10yo alone at 4am. It most likely would be OK, but if they woke up and had an issue and became distressed, that can have a significant effect on their confidence. On the tiny chance that there is a major issue, the consequences could be devestating.
DH takes himself or gets taxis for impractical airport trips. There have been some awkward drop-offs that I've helped out with because of a lack of options, but generally he sorts his own transport (he does a lot of short haul work flights with early starts)