It'll be the airlines that make that decision, not the airports. No doubt they chose those flights that cost them the least money to cancel, though I don't know what criteria they use to calculate that...
As one United Pilot told me once "Unless the Airport is closed, the plane is out of service or some sort of odd event they do try to keep International flights moving because if they were cancelled you'd have people stranded on both sides without an easy way to reroute them."
AFAIK airlines tend to cancel those short haul regional flights first during weather disruptions when limited flights are permitted for landing/takeoff before canceling the longer domestics and international.
They'll first cancel the flights heading to other airports also affected by the snowstorm. The last flights that will be canceled are flights to the hub where the same plane will be used on another flight.
Programs: Over-Entitled COdbaUA-1kMM, HH Plebe, Giving Tootsie Pops to UA employees, & a retired hockey goalie
Each airline will make their own decision to cancel a flight based on things such as weather, if an airport is open or closed, crew, mx and etc. Keep in mind that if a flight is cancelled, that means that aircraft can't continue on to it's onward location thus leaving two groups of pax stuck (those on the cancelled flight plus those waiting for the their flight) and when it comes to an airline that flies both domestically and internationally, unless there are "issues" at international locations (i.e. snowmageddon and/or volcanos in Europe), international flights are generally the last to be cancelled
It's raining hard. Your flight is canceled. But many of the other flights at your gate pull out and depart anyway.
Researchers at the University of California at Berkeley say they've figured it out. They dug through the paperwork airlines filed for 8,269 delayed domestic flights. The researchers crunched the numbers and found that half-empty flights are much more likely to be canceled during foul weather than full flights.
But it gets worse: Your flight is more likely to be canceled during a storm if you have fewer business class passengers on board than other planes at the gate do.
When Dr Jing Xiong factored in each plane's average ticket price, she found that airlines may discriminate against flights with lots of passengers who bought discounted tickets. She showed that flights on one airline with full business class sections were rarely canceled, while flights stuffed mostly with economy class passengers were often grounded.
While it's the job of the FAA and air traffic controllers to decide how to make the best use of airspace during weather delays, airlines are often given chances to decide which planes should be grounded and which ones should fly. The total money spent by the passengers on tickets appears to be one of the things an airline keeps in mind when canceling a flight.