Airlines canceled more than 4,400 flights as extreme cold in the U.S. Midwest and Northeast froze fuel lines to airplanes and posed exposure hazards for employees working on the tarmac.
JetBlue Airways took the most drastic step of any airline by suspending all flights at New York and Boston airports on Monday, with plans to gradually resume them on Tuesday.
The brunt of Monday's 4,400 cancellations was felt in such areas as Chicago, Minneapolis and Cleveland, according to the FlightAware.com tracking service. More than 1,600 flights were halted at Chicago O'Hare, an airport that typically has 2,400 daily flights, according to city officials.
"Even though there is not a lot of precipitation falling, extreme cold weather can severely impact operations," Andrea Huguely, a spokeswoman for American Airlines Group, said in an email.
American and American Eagle canceled more than 500 flights on Monday, roughly 14 percent of their typical daily count. At O'Hare, American had "minimal operations" and canceled nearly 380 flights, including American Eagle flights.
"The problem we—and other carriers—faced very early is the fueling pumper trucks wouldn't work," said American spokeswoman Mary Frances Fagan. "Parts were frozen. Fuel nozzles were also frozen and had to be taken to a hangar to thaw out. It's slow going."
(Read more: Thousands stranded by series of storms)
JetBlue said halting its flights at John F. Kennedy International, LaGuardia, Newark Liberty and Boston Logan airports would allow time to position flight crews and take other steps to recover from snowstorms that had struck the Midwest and parts of the Northeast. It said it would add extra flights on Tuesday and Wednesday to accommodate passengers whose plans were disrupted.