CHICAGO — Heavy fog stopped traffic at Midway Airport this morning and caused cancellations and long delays at O'Hare International Airport

"We're fogged in on every front," said Lisa Howard, a spokeswoman for the city's Aviation Department. O'Hare, the nation's busiest airport, is a hub for a large segment of the nation's East-West air traffic.

Many inbound flights were 30 minutes to an hour late at O'Hare, Howard said. United Airlines canceled 14 flights from O'Hare, and there were scattered cancellations by other airlines, she said.