The ground stops, which also affected the airport serving Richmond, Va., were expected to last until at least 8 p.m., according to the F.A.A., which said the smell had affected air traffic controllers.

The Federal Aviation Administration issued a ground stop for the three major airports serving Washington, D.C., and Baltimore on Friday, citing a strong chemical smell that it said was affecting air traffic controllers.

Flight traffic was stopped around 4:50 p.m. at Ronald Reagan Washington National Airport, Washington Dulles International Airport and Baltimore-Washington International Airport, according to the F.A.A.’s website.

Transportation Secretary Sean Duffy said on social media that the ground stop also included Richmond International Airport.

The ground stops were issued because of a “strong chemical smell at the Potomac TRACON that is impacting some air traffic controllers,” an F.A.A. representative said in an email, referring to a regional center in Warrenton, Va., that directs traffic headed to and from the Washington area.

Mr. Duffy said the F.A.A. was trying to pinpoint the source of “a strong odor” coming from the Potomac TRACON.

Flights are expected to resume around 8 p.m., according to the F.A.A.’s website.

Grace Wilkins Maxwell was on her plane at Washington Dulles International Airport to Louisville, Ky., for about an hour before passengers disembarked.

Passengers were at the gate, charging their phones and waiting for news, Mrs. Maxwell said. “I’m not convinced anyone is leaving D.C. tonight,” she said.

She was trying to get to Louisville to pick up her dog, Browser, a Brussels Griffon, who was in a dog show this week.

Mrs. Maxwell, who is from Richmond, Va., was going to wait a few hours and then possibly take a train home, she said.

“It seems like it’s expanding,” she said. “If it was minor, it would’ve already been fixed.”

(http://www.autoadmit.com/thread.php?thread_id=5845311&forum_id=2...id#49741314)