Parent is right. I've been in and around the SF Bay Area for about a decade and SFO is _only_ ever, unambiguously, the airport.
“Spending next weekend in SEA then staying with friends in MPS before returning home to SFO.”
So no, SFO is not only ever unambiguously the airport.
I believe the combination of more frequent flying, booking tickets ourselves online (rather than by telephone) and increased communication on devices have combined to result in this quirk of language.
Inside the city that's not always the case, but even when you're abbreviating sports teams and the like, it's common to use the airport code to refer to the city name if they match up so well.
It’s pretty American to think like that.
[1] https://www.flysfo.com/about-sfo/airport-commission/city-cha...