I am a nuke engineer, working in the electronics field, but I have to disagree that it's too complex or difficult to engineer a redundant grid support for an airport, including all the various feeds to various users.
We design things like this for nuclear power plants regularly. Also, for NYSE, CBT, and other financial institutions that are pretty much guaranteed zero electrical outage. We've had data lockouts, and network interruptions, but I can't recall the last time NYSE was affected by an actual power outage.
Sure it's a big calculus, and sure it's costly, but the alternative is staggering costs on failure. I work regularly with shunt battery backups, and motor gen systems that ensure way over five 9s reliability. It's also in hospitals.
Staged load shedding would include - commercial retail services in terminal, air cond/handlers(because they suck a ton of watts), lighting, etc. The critical path equipment like the network gear, computers, reservation systems would all be on local battery backups with generators behind them.
Taking out all the power from the whole structure in an airport by SPOF is pretty bad systems design. Wondering if our other massive hubs suffer the same limitations?