The U.S. Federal Aviation Administration on Friday night lifted a ground stop that had halted traffic at the three primary Washington-area airports for several hours after air traffic had to halt work because of a strong chemical smell tied to a circuit board that overheated.

The FAA said the issue disrupted operations at Potomac Consolidated Terminal RADAR Approach Control, which controls airspace over numerous airports in the Washington region.

The issue had earlier prompted the FAA to stop traffic at Reagan Washington National Airport and Washington Dulles International Airport in Virginia and Baltimore-Washington International Airport in Maryland, all serving the Washington area. The ground stop also affected Richmond International Airport in Virginia.

Flights began resuming around 8 p.m. after more than two hours of halted flights. Departures were facing delays of one hour to more than three hours on average at the three Washington-area airports.

Delays were impacting more than 325 flights, or 34% of arriving and departing flights at Reagan National Airport, about 30%, or 215 flights, at BWI and more than 260 flights at Dulles, according to FlightAware, a flight tracking site.

Transportation Secretary Sean Duffy said firefighters responded to the issue at the Virginia FAA facility and "confirm there is no danger to air traffic controllers, and they are returning to the Potomac TRACON. The source of the strong odor was traced to a circuit board that overheated, and it was replaced."

The issue snarled traffic during the busy U.S. travel period when students are on spring break. Airborne flights were diverted and dozens of aircraft on the ground were held in place, according to Flightradar24, a flight tracking site.