I've heard the airports have more detail?

Is this true?

What do you mean by that?

I know one thing:
If you decrease some "display" option, some facilities or buildings will disappear.

Sorry, things like taxiway textures, building textures etc...Believe me i know all about bad framerates - my graphics card is an SiS 630/730. It handles the game surprisingly well even with full graphics but it doesn't have anti-aliasing so objects can appear like they've been cut out roughly with a saw. But go somewhere like Heathrow and it's crap!