I suspect they mean that inbound flights from international airports may still take off (probably in part because the FAA can't _really_ stop them, in part because the volumes are much lower and thus more manageable, and in part because one might hope that by the time it takes to get to the US from many international destination, the incident will be resolved).

Very unlikely that any international flights bound for the USA are taking off. Probably many are turning around or diverting if they are not more than halfway there.

I'm not following this very closely, but I've not seen any reports of diversions for domestic flights, so I think it'd be unlikely for international flights. The report is just for a ground stop, which is just a stop in departures; normally a ground stop would allow flights already in the air to travel to their normal destination.

That reasoning doesn't really make sense. A flight from outside the US that is inbound could divert to a non-US airport that isn't impacted by whatever is going on, depending on where they are and what their fuel status is. A domestic flight doesn't have a non-US airport to divert to.

(Sure, a flight near the Canadian or Mexican border could in theory divert to a Canadian or Mexican airport, but it's unlikely many people on those flights have their passports with them.)

Ah, my point was more that if the action being taken isn't "get planes on the ground _now_" and so the US airspace remains open for traffic already in the air, then it's unlikely they're trying to get international planes to either divert or return.

This definitely feels like 'unable to manage normal volumes at normal speed' rather than 'unable to manage anything.'

In which case freezing domestic (and the huge amount of load it contributes to ATC) but keeping international normal makes sense.

Of course... the side effect is the "fun" that creates for incoming international flights with domestic connections...

> (Sure, a flight near the Canadian or Mexican border could in theory divert to a Canadian or Mexican airport, but it's unlikely many people on those flights have their passports with them.)

There must be some procedures in place for this - I pretty regularly take domestic (Canadian) flights that pass over the US where I don't carry my passport.

A domestic US flight can still divert to Canada. There usually are special arrangements that allow people on a diverted flight to stay short-term while the situation is resolved, even if they don't have the required documents or visas.

they let eithad take off from boston like 40 min ago

And I assume it becomes case by case at some point because they eventually start running out of space on the ground at airports.

Presumably it means they may allow some international flights to the US to depart if they expect the issue to be resolved by the time they are in US airspace.

It likely means any inbound international flights can be told to turn around and/or land outside of the U.S. instead.

The intent around the ground stop is to reduce in-air U.S. traffic.

Makes me wonder if we'll see another "Operation Yellow Ribbon".

https://en.wikipedia.org/wiki/Operation_Yellow_Ribbon

Alas, the Canadian goodwill level may not be as high this time.

Doesn't seem like it; I've seen several international flights land in JFK alone since this started. (On the other hand, these might simply not have enough fuel left to divert to any non-US airport.)

Not in the industry, but I think ground stops might actually not be a regular/automated procedural thing for inbound international flights in the way that they are for domestic flights.

As for asking already airborne flights to turn around, those coming in over the ocean might simply not have a non-US alternate airport available with their fuel remaining, so that's often not an option.

Every flight over an ocean has a set of pre-planned diversion airports.

Yes, but most of them are not viable in the late stages of a flight. Planes aren't carrying enough fuel to cross an ocean for a second time; most don't even have the capacity.

Please suggest an appropriate international alternate for a plane just about to land in Denver with an hour of fuel remaining.

Alternate airports are picked based with regards to all kinds of contingencies (many of them meteorological), but "the US closes literally every airport" is not one of them.

That likely falls within the case-by-case basis the FAA mentioned, and would likely be allowed to land at a U.S. airport that has capacity.

I'm not aware of a requirement that you need to always be able to divert to a different country.

I think it's more mundane than that, I assume they mean that certain international flights will be turned around or redirected while others will complete their route. Say a flight just an hour underway London to New York might be turned around while one nearly at its destination may be allowed to land.

Depending on the nature of the disruption it may be they simply have drastically reduced capacity to handle traffic so landings may be much slower and they'll manage the traffic based on various priorities.

Probably just means that if you're less than halfway across the Atlantic, you can turn around and go back to Europe. I really wouldn't suggest reading too much into the phrasing.

An Eithad flight took off from KBOS after the ground stop

Flight EY8 from Boston to Abu Dhabi https://fr24.com/ETD6PX/429055e2

friend is flying from London to NYC and they were told they might need to land in Toronto.

So my guess this is what it means "case by case". Some which are close to destination would be manually routed, others will land in different places.

Exactly. London to LAX may land in New York or the first available airport, or may route somewhere else.

Some might be turned back, depending on how far they are in the journey, fuel, etc:

Maybe they mean inbound international flights may be allowed to take off from their origin, on a case by case basis. Usually a clearance is required to take off from both the origin and destination.

like you don't have enough fuel to fly back across the ocean they'll accommodate you I assume?