Although their article clarifies that this isn't about changing anyone's physical location, as a general point about flying to/from Canada, many of the affordable itineraries involve connections through US airports and/or overfly US airspace (in a way that gives the US at least some authority over those flights).

This is not true for all flights to/from Canada, of course, but it does add complexity, expense, and often travel time for people who want to deal with Canada while avoiding US authority.

> /or overfly US airspace (in a way that gives the US at least some authority over those flights).

Overflight of US airspace doesn't give the US authority over the people inside the airplane. And flights to Canada from Europe or Asia don't overfly the US, except perhaps Alaska, but that's of zero consequence.

US handles overflights and transfers differently from practically every other country out there. For overflight, TSA gets lists of passengers in advance, and runs them against the no-fly list - if you're on that list, you won't be allowed to board, even if your plane never even lands in US.

Overflight of US airspace does give the US authority to choose who is allowed on the plane, to require the airline to provide specified information to them through the passenger manifest, and to impose other conditions simply for being allowed to overfly. A person born in a plane overflying US airspace at the time of birth is a US citizen. An emergency landing of a flight overflying the US will often land in the US, and a plane ordered by US authorities to land while overflying has to comply. Lots of US influence in this area.

You're right that many direct flights between Canada and Europe or Asia don't overfly the US. Many of the affordable options are via US connections, however, and travelers from the rest of the world to Canada frequently overfly the US.

As for Alaska, it's very much a part of the US, to the level that everything I said above is true for flights which only overfly Alaska and none of the rest of the US.

>a flight overflying the US will often land in the US, and a plane ordered by US authorities to land while overflying has to comply. Lots of US influence in this area.

Is it possible that some people are afraid of being charged with "Conspiracy against the United States" [1] and that they have to wait a long time in the USA until a jury decides that they are innocent?

[1] https://en.wikipedia.org/wiki/Conspiracy_against_the_United_...

It's possible, sure. That's never been high on the list of criminal charges I've ever heard people worry about, but I'm sure it's relevant to some people.

"A person born in a plane overflying US airspace at the time of birth is a US citizen."

It's unclear (and doubtful) whether that is true:

"All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside."

Courts could probably use the jurisdiction language to say "nope". No idea whether there have been any court cases over this though.

The Constitution sets the minimum bar, but the legislature can grant citizenship beyond that.

I'm not sure whether it's due to a specific law, or courts applying 14A, but there's broad agreement that babies born in US airspace are, indeed, US citizens.

The jurisdiction language basically excludes parents with diplomatic immunity, under current rules, not other people flying above the US regardless of the aircraft's country of registration or any other status attributes of the parents.

In practice, what I said above is well-settled legal and administrative practice in the US, whether or not the constitutional words could have been interpreted or differently by Congress and/or the courts.

US authorities receiving proof of birth above the US and lacking reason to suspect parental diplomatic immunity certainly will and actually do grant proof of US citizenship, no further argument needed once the location of birth is documented.

ICAO disagrees, a child born on an aircraft is subject to the laws of the country the aircraft is registered in.

Although the registration country's laws do indeed generally apply on aircraft, that is in addition to what I said, not instead of it. Nationality laws can grant or withhold citizenship worldwide regardless of location and regardless of whichever other laws apply for most purposes.

For example, as an American who lived in the US for more than my first 30 years of life, any (biological) kid I have anywhere in the world will be a US citizen by birth, regardless of location, based solely on US law, even though outside the US I'm generally subject to the host country's laws and not to US laws. (Nationality laws are not the only US laws to have extraterritorial application, but the default rule is for US laws to apply domestically only.)

As an inverse example, the denial of US citizenship by birth to people born in the US to two diplomatically immune parents is solely due to US law, not due to any international agreement, even though the diplomatic parents are mostly immune to US law and subject to at least a large fraction of their home country's law.

Here's a general Wikipedia summary of how birth aboard aircraft and ships works for purposes of nationality, including specific comments on Canada and the US, as well as addressing the two international conventions that people often think are relevant to this question but aren't: https://en.wikipedia.org/wiki/Birth_aboard_aircraft_and_ship...

Very true, countries can deviate from this in the positive direction. So the US is free to grant citizenship to a lot more than these (e.g. anyone born with at least one US parent, that's also what my country does), but it's not required by ICAO, it's a decision the US can make unilaterally.

Right. But it's more than that: there's no default from which to deviate in any direction. Every country can freely choose who it considers as its citizens under all circumstances regardless of which law usually applies where, and I don't think any treaties cover that (with some narrow and not-worldwide exceptions around people who would otherwise be stateless) including the ICAO ones. ICAO's rule for the "Lex loci" of airplanes is irrelevant to the nationality question except when a nation's domestic law of nationality makes it relevant for granting (or withholding) that nation's nationality.

The US nationality rule for birth outside of the US is narrower than "anyone with one US parent", by the way. It wouldn't apply to cases like mine if my time spent living in the US had been below a certain threshold. By contrast, even children born in the US to those whose presence in the US is unlawful or otherwise irregular are citizens by birth.

Citizenship is defined by the country that grants it.