Have to? Strictly speaking, no, not if they didn’t care who say or heard them… If they were hypothetically invading another NATO ally and wanted to minimize spillover, and they would do so reasonably easily, would they? Maybe.do they have to avoid our airspace?
Also, hypothetically if they had a couple battalions on C-17s that they wanted to sneak out dead of night for at least some tactical surprise, easier to do that flying northeast out of Alaska than crossing the eastern seaboard/Atlantic Canada and it’s quite busy and controlled airspace- and crossing right over Bagotville.
If Trump decided on a military option for Greenland and his senior military leadership supported, they would want a fair accomplice in one fell swoop.
~7 hours flight time in C-17s for Alaska to Nuuk, avoiding Canadian airspace. Sunrise in Nuuk is about 1030 local, 7 hour time difference between the two. Napkin math would say you take off from Alaska around 2000 local puts you over Nuuk for sunrise for an airdrop.
Do I think military invasion of Greenland is likely? I don’t. Is it plausible? Absolutely. If it happened, those troops out of Alaska would be a logical opening move in terms of conventional forces. And they could transit tactical aircraft by a northern route to Pituffik to stage and then press onwards.
A carrier, or an amphibious group with F-35s and the ability to secure a local airhead with SOF would make things a hell of a lot easier but probably wouldn’t be essential.
Now, if the Europeans reinforce with real substance, the math on dropping a couple airborne battalions in changes. And weather would matter a lot too.
Like I said, I don’t believe it’s likely. I wish it was more unlikely.
