Is there any historical basis for how the traffic to cut is selected? Future flights? Existing flights? Short domestic flights vs international flights?

It’s also unclear what the actual definition of ‘cut’ is

Yes, there's a well-established historical basis through Ground Delay Programs (GDP). The FAA uses "Ration-by-Schedule" delays are allocated based on your scheduled arrival time with adjustments for airline equity.

Flight selection: It affects flights already in the system (filed flight plans), not future bookings. The scope is defined geographically all flights within X miles or specific air traffic control centers get hit proportionally. There's no inherent bias toward domestic vs international; if you're in scope, you're in scope.

What "cut" means: They reduce the Airport Acceptance Rate (AAR) the number of aircraft the airport can handle per hour. So instead of 60 arrivals/hour, maybe it's 54. Your flight gets assigned an Expect Departure Clearance Time (EDCT) basically "don't take off until this specific time" to meter the arrivals.

The system prioritizes keeping planes on the ground rather than having them circle the destination airport burning fuel. Late-filing flights (cargo, charters) get assigned the average program delay first, then compete for any remaining slots.

So if you filed a flight plan to LaGuardia and there's a 10% cut, you're getting a controlled departure time calculated by the Flight Schedule Monitor software based on your original schedule, airline equity, and current delays.

Of course, that assumes that this won't be politicked. I would not at all be surprised to see them kneecap NYC, Chicago and any other cities that are doing something the current white house doesn't like.

The sibling comment has a more structured reply to the whole process, but of note the article specifically mentions the FAA has exempted international flights.