Not for the first time either, as Reuters reminds us in this brief report on the disruption in US flights this morning, but this one wasn’t an equipment-failure fire. A fire in an Aurora, Illinois air-traffic control tower forced the cancellation of hundreds of flights in and through Chicago’s O’Hare and Midway airports, creating ripple effects throughout the country:

CNN reports from the airport itself, and notes that police and FBI are investigating the incident as arson, but not terrorism. One suspect is already in custody:

Mystery surrounded the interruption, as authorities reported not only that a fire closed the Federal Aviation Administration control center in Aurora, Illinois, but also that a man was found with self-inflicted wounds there.

Responders found a person suffering from cuts to at least one wrist, two law enforcement officials told CNN, citing initial reports from investigators. The person is being treated and questioned about the fire, which appears to have been intentionally set, the officials said. Investigators believe the person tried to commit suicide, the officials said.

The fire is not believed to be a terrorism act, Aurora Police Chief Greg Thomas told reporters. It appears to have been set by a contract employee, he said. Two people were injured: the male suffering from self-inflicted wounds and a man, 50, who was treated at the scene for smoke inhalation, Thomas said.

From the initial statements, it sounds as though the issue may be an unstable contract employee, which is better than an act of terrorism …. but still. Doesn’t the FAA keep an eye out for that sort of issue, especially in high-tension environments such as air traffic control centers?

In May, smoke from a failed air-conditioner motor spewed smoke inside a radar facility, forcing a similar shutdown in Chicago air traffic. This time, the number of canceled flights hit 580 by 8:30, although operations are expected to return to normal shortly:

Thomas Ahern, a spokesman with the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, told CBS Chicago that the man suffered burns and knife wounds. Ahern posted to his Twitter account that the bureau was at the scene of the fire as part of a county fire investigation task force.

An employee of the facility was treated at the scene for smoke inhalation and the fire was extinguished by 7 a.m., according to Ferrelli’s email.

By 8:30 a.m., more than 580 flights at O’Hare and Midway had been canceled, according to aviation tracker FlightAware.com. FlightAware.com CEO Daniel Baker said the number of cancellations and delays are expected to rise considerably over the next few hours. Southwest Airlines suspended all flights at Midway until noon, according to the Chicago Department of Aviation.

The airlines have continued to check passengers in for flights, so the expectation is that the disruption will be temporary. Thanks to the large number of connections made at O’Hare and Midway, though, passengers around the country may have a very long day of travel ahead of them. Be sure to check with your airline to see whether you can take a couple of more hours to get to the airport.