Airlines have canceled thousands of flights in the United States due to winter weather

(CNN) — Airlines are still recovering from an intense day of storms that slammed into the eastern United States on Friday and saw every state under some form of weather-related warning.

As of Saturday afternoon, more than 1,200 flights had been canceled and 4,700 flights delayed in the United States, according to data from tracking site FlightAware. While that’s a significant improvement from Friday’s nearly 2,300 cancellations and 9,000 delays, airports in the Midwest and Northeast continue to experience significant travel delays.

In Michigan, where more than 140,000 customers are currently without power, the Detroit Metropolitan Wayne County Airport delayed 40% of its departing flights. New York’s Buffalo Niagara International Airport has canceled 60% of its flights. Airports in Denver, Boston and Chicago are also experiencing delays. About 550 flights in and out of Chicago O’Hare International Airport have been postponed. Denver International Airport, where temperatures dropped dramatically Saturday night, had the second highest number of cancellations.

These travel delays add to an already difficult week for airlines and their passengers. Last week, more than 200 United and Alaska Airlines flights were canceled each day due to federally ordered grounding of Boeing 737 Max 9 planes. The Federal Aviation Administration issued the order after a piece of fuselage flew off an Alaska Airlines flight with 177 people on board on January 5. The incident left a gaping hole in the side of the plane and ripped headrests from the seats while the plane was flying at 16,000 feet shortly after takeoff from Portland, Oregon.

United and Alaska Airlines, the two largest US airlines that use Max 9 aircraft, are among the airlines with the most flight cancellations, according to FlightAware. United topped the list by canceling about 250 flights on Saturday, about 10% of its fleet. Alaska Airlines experienced the fourth-highest number of cancellations, with nearly 120 flight cancellations.

Both airlines said last week that they had canceled all flights of their Max 9 planes through mid-January.