Pretty sure that’s the FS2024 streaming process at work (or rather, not working). I’ve flown into and out of the stock KLGA and the generic auto-gen airport loaded in fine. Of course, after the first couple days I started linking my Community content in and have been using MK Studio’s KLGA instead, but before then KLGA autogen buildings were there for me.
I did have issues with most of KSEA not loading in for like two days in a row. However, I flew out of there Sunday and it was fine. Again, I suspect server/content streaming issues with stuff like this.