As if the roads and airports weren't busy enough with holiday travel, the weather fogged up travel plans Thursday morning.
The National Weather Service issued a dense fog advisory for the Washington area until 9 a.m. Drivers were warned to use headlights, drive slow and keep distance between vehicles as visibility was reduced to less than a quarter of a mile.
Fog also delayed some flights heading to the Washington and Baltimore areas. The Federal Aviation Administration said the fog prompted a ground stop for flights arriving Thursday morning at all three Washington-area airports. Departing flights apparently were not affected.
A spokesman for Reagan National Airport said the fog cleared enough by 8 a.m. to allow some flights to land. But it continued to cause delays at Dulles International Airport.
A ground stop also was issued for Baltimore-Washington International Thurgood Marshall Airport.