A United flight arriving at Washington's National Airport was isolated on a runway around noon on Tuesday after reports of a bomb on board, according to reports.

The major international airport was hit by a ground stop.

CNN correspondent Pete Muntean said sources had told him a bomb threat had been received.

It's the third time in the past week that the FAA issued a ground stop. Planes that were about to take off were returned to the gate, the plane-tracking site Flight Radar showed.

Upon landing, the affected flight was isolated to the eastern part of the runways near the Potomac River.

WUSA News began airing a live stream showing police cars rushing to the plane. After about half an hour, buses approached and steps were rolled over to the plane. People then began deplaning.

Airborne flights appear to be holding or diverting to alternate airports, Air Nav Radar posted on Facebook. At least one Southwest flight was diverted to Baltimore. Others appear to be flying to Dulles Airport.

The incident came mere moments after Transportation Secretary Sean Duffy warned that there will be "chaos" in the coming weeks due to the shutdown and the shortage of air traffic controllers and TSA agents.