More than 7,000 U.S. flights were delayed and nearly 900 canceled on Sunday as thunderstorms snarled air travel in and out of some of the country’s busiest airports and the Federal Aviation Administration briefly halted departures to major airports serving Washington D.C., citing repairs to a power panel needed at an air traffic control facility.

Shortly after 6 p.m. ET, the FAA issued ground stops for Baltimore/Washington International Thurgood Marshall Airport, Ronald Reagan Washington National Airport and Dulles International Airport, preventing aircraft from taking off for those destinations. It lifted the orders within an hour.

“Departures to D.C.-area airports have resumed and repairs to the communications power panel are complete,” the FAA said in a statement. “During the repairs, a back-up system handled communications safely.” Delays at Washington Dulles were averaging around 90 minutes as of 7:15 p.m.

Throughout Sunday, weather caused delays at airports from Miami to Boston to Detroit.

More than 440 flights to and from Newark Liberty International Airport were delayed. The airport is a major hub of United Airlines, which had more than 840 delayed flights Sunday, according to FlightAware. American Airlines posted 938 delayed flights, 27% of its mainline schedule, Delta Air Lines had 716, or 20% of its schedule, and New York-based JetBlue Airways had 472 delays, or 45% of its planned schedule.