Most flights out of Baltimore-Washington International Thurgood Marshall Airport were canceled Monday evening and night because of thick fog across the region, according to an airport spokesman.
The "extensive flight cancellations," including arrivals and departures, forced many holiday travelers to begin reorganizing their schedules.
It was the rare flight that wasn't canceled at the airport, said Jonathan Dean, the BWI spokesman.
The Federal Aviation Administration at times imposed air-traffic restrictions, Dean said.
The National Weather Service first noted fog moving into the region Sunday, and had issued a dense fog advisory for much of the Baltimore area until 6 a.m. Tuesday.
Travelers were told by the airport to check with airlines for their flight status or to rebook a flight.
Baltimore Sun reporter Scott Dance contributed to this article.