At least 878 flights were canceled in the United States early on Wednesday, with the departures from the busy hubs of Chicago, Denver and Atlanta leading the list of the most cancellations, according to a flight-data tracker. 

Another 404 flights had been delayed as of about 5 a.m. ET, according to FlightAware. 

Chicago O’Hare International topped the tracker’s list of cancellations, with 44 as of about 4 a.m. local time. Next was Denver with 43 and Atlanta’s Hartsfield-Jackson with 37. 

Wednesday’s flight cancellations appeared set to continue a dayslong streak of chaos at American airports, which were operating under duress amid a federal government shutdown.

The Federal Aviation Administration continues to limit capacity at 40 major U.S. airports. Many federal employees, including Transportation Security Administration staffers, were working without pay as the partisan impasse dragged on in Washington.  

This is a developing story. Please check back for updates.