US domestic flight crosses into Canada - what is the legal situation?
<p>It's common for US domestic flights to cross into Canadian or Mexican airspace. For example, a flight from Alaska to New York, Seattle to Boston, or Hawaii to Texas would likely cross into foreign airspace.</p>

<p>However, as far as I know, this is not legally considered a border crossing. In my experience, there is no passport control.</p>

<p>What exactly does the law say about this? What is the determining factor of a whether border crossing has occurred when air travel is involved?
Can <a href="https://www.aclu.org/blog/national-security/cbp-cant-detain-domestic-flight-passengers-refusing-suspicionless-id-checks" rel="noreferrer">CBP check passenger IDs on domestic flights</a> that crossed into foreign airspace?</p>

<p>Furthermore, if an domestic flight made an emergency landing in another country, what would happen to the passengers who don't have their documents with them? Is there a special legal provision for such scenarios?</p>

<p>On such a flight whilst it's overflying non-US airspace (not necessarily airspace over the U.S.A. proper, as the U.S.A controls airspace outside its own sovereign territory), then it is classed as being in the international airspace of the country that controls it e.g. Canada, or Mexico. As such, in the event of an emergency landing, then any passengers without suitable documents would most likely be returned to the country that they came from e.g. the USA.</p>
<p>Hopefully the authorities of that country e.g. the USA would then be able to let them back in, however this could get complicated because you aren't supposed to take luggage with you when evacuating an aircraft in an emergency. I honestly have no clue what the U.S. Authorities would do with someone who was returned to the U.S.A. from another country e.g. Canada, or Mexico, with no documents whatsoever in that scenario.</p>

united-states immigration air-travel borders