The disruptions began when police and firefighters arrived at the Federal Aviation Administration’s Chicago En Route Center in Aurora, Illinois, one of the busiest U.S. air traffic-control facilities, after receiving a call about smoke coming from the building, said Dan Ferrelli, a spokesman for the city.

“We found a contract employee suffering non-gunshot related self-inflicted wounds,” Ferrelli said. The employee, whose name wasn’t provided, started the fire and is being treated at an area hospital, Ferrelli said.

The building, in a city about 40 miles west of Chicago, was evacuated. The facility oversees high-altitude traffic across Midwest states including Illinois, Indiana, Wisconsin and Iowa.

The worker may have used gasoline to start the fire and had burns and cuts on his hands and arms, Tom Ahern, a spokesman for the Chicago office of the Bureau of Alcohol, Tobacco and Firearms and Explosives, told the Chicago Tribune.

‘Disgruntled Employee’

Early indications were that he was “possibly a disgruntled employee,” the newspaper reported.

One of 20 en route air traffic control centers in the country, the Aurora facility monitors flights that are beyond 30 miles or 40 miles of an airport and typically above 15,000 feet, said Gregory “Sid” McGuirk, a professor at Embry-Riddle Aeronautical University in Daytona Beach, Florida.

Such a facility probably would have 90 to 100 people on duty during a normal day shift and might be expected to monitor as many as 15,000 flights per day, said McGuirk, who spent 25 years working in an FAA en route center.

There were about 15 to 30 people evacuated from the Aurora building when the incident occurred, according to Ferrelli. A 50-year-old man suffering from smoke inhalation was treated at the scene.

About 44 percent of departing flights at Chicago’s O’Hare International, the second-busiest airport in the nation, were canceled, and 75 percent of Midway’s, according to the tracking website FlightAware.com.

Damaged Equipment

Overall, airlines had canceled 1,826 flights in the U.S. as of 1:16 p.m. Chicago time, according to the website. That’s still short of the disruptions associated with heavy winter snowfalls, such as the 7,100 trips scrubbed on Feb. 13, the most in the U.S. since 2012’s Hurricane Sandy.

The length of today’s disruption will depend on whether there’s damage to equipment in the center, John Hansman, an aeronautics and astronautics professor at the Massachusetts Institute of Technology, said in an interview.

“If it gets fixed by tonight, then it will be sort of a blip,” he said.

What distinguished today’s incident was the way in which the disruptions were centered on Chicago. Weather-related cancellations and delays typically affect an entire region’s worth of airports, socking in the Washington-to-Boston corridor or the big Midwest airport hubs in Minneapolis, Chicago and Detroit.

$1,500 Ticket

For now, there are very few ways to get out Chicago.

Jose Galindo, 36, sitting on the floor of a United terminal at O’Hare, said “there’s thousands of people trying to purchase a ticket.”

Galindo has been trying to buy a ticket online after his Delta flight to Atlanta got canceled. He said he laughed when he found a one-way flight with a connection to Houston on United for almost $1,500.

Controllers in other locations are managing the flights from elsewhere that still need to pass through the airspace. No landings or departures at O’Hare or Midway are being allowed.

Ticket agents at Washington Ronald Reagan National Airport had notified passengers of the delays, which led some customers to improvise alternative arrangements. Ticket agents were pessimistic that flights would resume in time to accommodate the waiting passengers.

As passengers sought to rebook, they were told that flights to Detroit, Indianapolis and any city within a four-hour drive of Chicago were already sold out.

Federal Investigators

“Disappointment to say the least” said Martha Szeezil, 73, describing her reaction to her canceled flight while waiting behind about 35 people in front of the United counter at O’Hare. Szeezil had been standing in line for about an hour and a half to rebook her return flight to Tampa after visiting relatives in Chicago.

The Aurora police have yet to publicly identify the man who they say is believed to have started the fire. No criminal charges have been filed, Ferrelli said.

The incident is being investigated by a joint task force of the FAA, the Bureau of Alcohol, Tobacco, Firearms, and Explosives, the Federal Bureau of Investigation, and the Aurora police, a police spokesman said.

“This is not a terrorist-related incident,” Ferrelli said.

Flights to the region were disrupted in May after a fire broke out in a separate air-traffic facility in Elgin, Illinois, that handles flights within about 50 miles of Chicago.
–With assistance from Michael Sasso in Atlanta and Elizabeth Campbell in Chicago.