(CNN) -- The effects of an employee's alleged sabotage of the Illinois air traffic control center where he worked continued to be felt by air travelers through the weekend.
By Saturday afternoon, more than 660 flights scheduled to either take off or land at Chicago's O'Hare International Airport were canceled, according to the Chicago Department of Aviation. Another 120 had been canceled over at the city's Midway Airport.
The disruption stems from a Friday morning fire at the FAA Chicago En Route Center in nearby Aurora, a critical air traffic control center.
Police say that blaze was set intentionally by Brian Howard, a contract employee at the facility, before he apparently attempted to kill himself.
An FBI affidavit says that a first responder saw some feet sticking out from under a table and found a shirtless Howard "in the process of actively slicing his throat with another knife."
He told paramedics to "leave me alone," the affidavit said.
He survived and was taken to an area hospital. His condition was not available Saturday.
He's charged with one count of destruction of aircraft or aircraft facilities, a felony that could land him a 20-year prison sentence.
No court date has been set.
Ominous Facebook message
According to the FBI, Howard, 36, had worked at the center for eight years but was facing a transfer to Hawaii.
In a private Facebook message sent to a relative just before the fire, he wrote "Take a hard look in the mirror, I have," the message said, according to the affidavit. "And this is why I am about to take out ZAU [the three-letter identification for the control center] and my life. ... So I'm gonna smoke this blunt and move on, take care everyone."
Then, at 5:40 a.m., Howard -- who worked in "telecommunications matters," according to the FBI -- apparently started the fire in the control center's basement, causing the facility that controls flights in several Midwest states to evacuate and shut down.
The effects were immediate.
O'Hare -- the second-busiest airport on the planet according to Airports Council International -- is a main hub for United Airlines and other major carriers, with flights headed to international destinations. When controllers stop flights scheduled to there, it has the potential to trigger a line of falling air-traffic dominoes that will ruin travel plans for countless would-be passengers.
By Friday evening, more than 2,000 flights had been canceled in and out of Chicago's two airports.
The ripple effect caused disruptions at airports across the nation. Southwest Airlines suspended all fights Friday not only in Chicago, but at Milwaukee's General Mitchell International Airport as well. Hartsfield-Jackson Atlanta International Airport had 70 cancellations and there were 56 at New York's LaGuardia Airport.
FAA divvies up Chicago air traffic control
The FAA said that a clean-up crew was brought in Saturday "to begin drying out water-damaged equipment" in the telecommunications room where Howard set the fire, as well as to clean and sanitize the area after the attempted suicide.
But just when ZAU will be fully operational again is not yet known.
"Technicians also are completing a thorough damage assessment and timeline for restoration of services," the agency said Saturday. "The FAA is using all the tools at its disposal to safely restore as much service as quickly as possible."
The FAA said over the weekend that it was managing the air traffic in and out of Chicago "through other large Terminal Radar Approach Control (TRACON) facilities in Illinois, Indiana and Wisconsin with additional help from high-altitude centers in Minnesota, Kansas, Indiana and Ohio."
In the meantime, the FAA said ZAU's displaced employees "are assisting at the TRACON facility in Elgin, Illinois and other air traffic facilities."
CNN's Ralph Ellis, Jason Hanna, Thom Patterson, Mike Pearson, Amanda Watts, and John Newsome contributed to this report.