WASHINGTON—A technical problem at a Virginia air traffic control center that caused flight delays and cancellations throughout a large swath of the Northeast on Saturday has been resolved, the Federal Aviation Administration said.

Delays began building about 9:45 a.m. EDT, according to FlightRadar24, a flight monitoring website. Flights bound for airports in the Washington area were some of the most affected, including Washington’s Reagan National Airport and Dulles International, as well as Baltimore-Washington International...