The idea that airports (or the transit areas of airports) are somehow extraterritorial and not part of the sovereign territory of the nation where they are located is a popularly-held belief which is entirely untrue. You'll notice that police of the host nation operate in these areas for example. For example, see https://english.elpais.com/elpais/2013/06/27/inenglish/13723... but there are hundreds of sources for this if you search online.

US airports don't have a transit area. Anybody transiting through the US has to go through immigration/customs.

Wait... so you need a USA visa just to fly a route that goes via the USA, even if you never leave the airport?

That seems... suboptimal.

All it takes is a corridor from arrivals to departures to allow people to leave again on a different plane out of the country.

Yup, plus you pick up your bags, go through customs and recheck your bags after landing at the first US airport. Same for Canada AFAIK.

Sometimes you don’t have to re-check your bags.

Some US airports and airlines are like that for some flights (e.g. international delta flight to Detroit and then onward to Canada). Finally US customs figured that there’s less to worry about if you just hold onto my bags instead of forcing me to pick them up.

Good to see some progress there!

> Wait... so you need a USA visa just to fly a route that goes via the USA, even if you never leave the airport?

Yes. There are some details at the following article: https://en.wikivoyage.org/wiki/Avoiding_travel_through_the_U...

There’s no separate international departure area and domestic departure area in US airports. Therefore, it takes a lot more than a corridor.

Thanks , I did not know that. I thought that every international airport had one.

Transit areas are still subject to local laws. If I ran an online shop selling, say, firearms to Britons or Nazi flags to Germans I would not expect to pass through their airports unmolested.

If you're not going to USA/any other country and you don't have a VISA for that country But the airplane is forced to land that makes an involuntary illegal alien. The flight was forced to land, he knew he could not visit the USA