Flight cancellations skyrocketed over the weekend due to snowstorms in Chicago, Denver and other parts of the country.

According to flight-tracking website FlightAware, more than 2,300 domestic flights were canceled by Sunday afternoon while 4,279 were delayed. The spike in cancelations comes at a time when many travelers were returning home from the holidays.

On Sunday morning, Chicago’s O’Hare International Airport already was accounting for 265 outbound flights canceled and Chicago Midway International Airport had 41 outbound flights canceled.

Along with 252 flights headed to O’Hare and 22 coming into Midway also getting canceled. Major airports Denver, Detroit and Newark, New Jersey, each had over 100 cancellations.

Southwest Airlines, which often flies through Chicago, had to keep 411 flights on the ground, according to flight information from 11:30 a.m. Sunday.

Many other major airlines saw cancellations. JetBlue had canceled 169 of its Sunday flights. Delta had 162 cancellations, while American had 144, and United had 101.

Flights were also heavily disturbed over the weekend in the D.C. area for Reagan National Airport with 22 outbound flights canceled. Thurgood Marshall Baltimore-Washington International Airport had 12 outbound flights canceled. Washington Dulles International Airport had 17 outbound flights canceled.

SkyWest Airlines reported a total of 477 cancelations.