The first amendment is indeed concerned only with the US government’s interaction with the matter, as is appropriate, but that does not imply it’s without other limitation. Your list is very broad and covers a wide range of common sense limitations—like, say, that you don’t want somebody in your vehicle harassing you.

Anyway, airlines are hard because the basic problem is they’re public necessity still halfway regarded as private business. It’s also an unnatural situation that many people be forced to share such little space in “public”, and we’d likely have a different constitution were it always the case.

I don’t think this one will be addressed by principle from on high.