A view of Chicago's O'Hare International Airport.

(Ercan Karakas/Creative Commons)

The number of flights canceled at Chicago’s Midway and O’Hare airports ahead of possible thunderstorms rose again by the afternoon.

The Chicago Tribune reported that by 3:30 p.m. as many as 800 flights were canceled between both O'Hare International and Midway Airports.

Although Chicago isn't under a severe watch, severalsevere thunderstorm watcheshave been posted for parts of the southern Plains and Midwest.

(FORECAST: Severe Weather Threat)

Passengers on flights that weren't canceled should still expect a long day and possible delays.

Chicago airports are still recovering from a fire at the air traffic control center in Aurora last week. An FAA contract employee, Brian Howard, faces federal charges in connection with the fire.The Associated Press reportsflights operationsbetween 80 and 85 percent for O'Hare and Midway.

NBC Chicago reports the Chicago En Route Centerin Aurora expects to be fully operational by Oct. 13.

MORE ON WEATHER.COM: The World's Busiest Airports