Chicago flights halted by fire 'set by air safety worker'
A fire in an air traffic control facility that grounded all flights in and out of Chicago's two major airports was set by an employee, officials say.
Brian Howard, 36, has been charged with one count of destruction of aircraft or aircraft facilities in connection with the fire in the building's basement.
Mr Howard was found with burns and self-inflicted wounds. Investigators say he used petrol to light the blaze.
By Friday afternoon flights in and out of the airports were slowly resuming.
More than 850 flights were cancelled in Chicago alone and many already in the air were redirected.
In a statement, the FBI said Mr Howard was charged on Friday but remained in hospital recovering from his injuries. No court date has been scheduled.
"We believe he set the fire and he used some kind of accelerant," Aurora Police Chief Greg Thomas said in a news conference on Friday.
The building was damaged by the fire and the water used to extinguish the blaze.
Officials said they did not yet have a possible motive for the act but said Mr Howard was a contractor for the Federal Aviation Administration (FAA) and was authorised to be in the building. He had no ties to terrorism.
The fire broke out just before 06:00 local time (11:00 GMT) on Friday morning in the Aurora, Illinois, air traffic control building, 40 miles west (64km) of Chicago.
Air traffic control officials said the radio frequencies with which they worked went dead and the control system was immediately shifted to a back-up system, the Chicago Tribune reported.
Workers used the back-up system until they were forced to evacuate.
"The [radio] frequency failed," a unnamed controller told the newspaper. "Depending on how bad the fire was, it could be a real mess getting things back to normal."
One man was treated for smoke inhalation at the scene but no-one else was injured.
FAA spokeswoman Elizabeth Cory said management of the region's airspace was transferred to another facility as the Aurora centre was evacuated.
By Friday afternoon, flights already on their way to Chicago were allowed to continue but landed at a slower pace.
Flights were taking off at a slower rate as well and air safety officials said they did not know when full service would be restored.