The deep freeze that’s spreading across much of the country is causing major disruptions for air travel.

More than 3,700 flights — about one out of every 10 domestic departures — were canceled by late Monday afternoon, the bulk of them in Chicago, Cleveland, New York and Boston.

With wind chills as low as 45 below zero at some airports, workers could only remain exposed on the ramp for a few minutes. That made loading and unloading luggage a challenge.

American Airlines said temperatures have been so cold at Chicago’s O’Hare International Airport that fuel and de-icing liquids are actually freezing. United Airlines says its fuel is pumping slower than normal in Chicago.

JetBlue Airways stopped all scheduled flights to and from New York and Boston on Monday. Southwest ground to a halt in Chicago, but by Monday evening, the airline said “a trickle” of flights had resumed.

In recent years, airlines have cut the number of flights to ensure most planes depart full. While that’s helping the airlines’ finances, it leaves very few empty seats to rebook stranded travelers, and sometimes, it can take days to get everybody to their destinations.

(AP)