(CNN) -- The man accused of setting a fire in an air traffic control center, causing the shutdown of operations at Chicago O'Hare International and nearby Midway Airport, sent a private Facebook message to a relative just before he started the blaze, the FBI says in an affidavit.
"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, 36-year-old Brian Howard apparently started the fire in the control center basement, the affidavit said. When firefighters arrived, they found him lying on the floor and slicing his throat with a knife, the affidavit said.
The FBI charged Howard, a resident of Naperville, Illinois, with one count of destruction of aircraft or aircraft facilities, a felony. Howard was taken to a hospital for treatment of his injuries.
The fire started at about 5:40 a.m. Friday and caused the evacuation of the air traffic control center in Aurora, Illinois, which controls flights in several Midwest states.
Airlines at O'Hare canceled 1,550 flights and 470 at Midway, the Chicago Department of Aviation said at 8:45 p.m. Friday. Southwest Airlines suspended all fights for the day at Midway and Milwaukee's General Mitchell International Airport.
The ripple effect caused the cancellation of flights at airports across the nation. Hartsfield-Jackson Atlanta International Airport had 70 cancellations on Friday, compared to seven on Thursday, according to Flightaware, a flight-tracking website. LaGuardia Airport in New York City had 56 on Friday and 10 on Thursday.
By Friday afternoon, flights to the Chicago airports had resumed at a "reduced rate," authorities said. The effect of the fire on Saturday's flight activity has not been determined and it was not clear when the center would reopen.
Faced transfer to Hawaii
Howard had worked eight years in the center but faced a transfer to Hawaii, the FBI says in an affidavit. The documents don't specify his job title but said he worked in "telecommunications matters."
The FBI said Howard arrived at the control center a little after 5 a.m. dragging a "hard-sided roller board suitcase" into the basement, where he usually worked. He allegedly sent the Facebook message about 30 minutes after arriving and the recipient notified police.
At 5:42 a.m. somebody in the control center called 911 about a fire, the affidavit said. First responders found smoke in the air, blood on the floor, exposed cables, burned towels, a gasoline can, a lighter and a knife on the floor, the affidavit said.
One paramedic 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," the affidavit said. Howard, the affidavit said, told the paramedics to "leave me alone."
Police obtained search warrants for Howard's home and found "legal documents that had been laid out in a staged manner, in an attempt to make them easier to find," the affidavit said. The affidavit didn't describe the documents.
No court date has been set for Howard. If convicted, Howard faces a possible sentence of up to 20 years in prison and a maximum fine of $ 250,000.
CNN affiliate WLS reported that Howard was a machinist mate in the Navy from 1996 to 2000 with nothing unusual about his military record. He had a few traffic citations in 2007, but nothing serious, WLS said.
"He seemed like an everyday, normal kind of guy to me," neighbor Colin McGrath told WLS.
Travelers are frustrated
When the two Chicago airports shut down, controllers at other airports helped manage traffic to and from Chicago.
O'Hare last year handled 883,000 takeoffs and landings, ranking it as the second-busiest airport on the planet, according to Airports Council International.
Travelers stood in long lines inside the O'Hare terminal trying to rearrange flight plans. They described a frustrating scene to CNN reporters.
"There's chaos mixed with outrage," said Bernard Thompson of Washington, D.C., who needs to be home by Sunday for a speaking engagement.
Thompson said that after his flight was canceled, the airline told him the next flight with an open seat would leave Monday. He booked a flight with another airline, only to discover the first airline couldn't locate his luggage.
"I'll get there but it's a question of whether I'll have my luggage with me," he said.
The fire ruined travel plans at other airports.
Des Moines International Airport reported 19 cancellations on Friday, according to Flightaware, including the flight that would have carried Chelsea and Bill Wright to New York City.
"We boarded our dogs and our kids are here and we got babysitters for them so it's messing everything up," Chelsea Wright told CNN affiliate KCCI.
Other control centers pitch in to help
In a typical backup plan for a disabled FAA center, the FAA could assign air traffic control authority to FAA centers in other cities, such as Indianapolis, Cleveland, Minneapolis or Kansas City.
Doug Church, a spokesman for the National Air Traffic Controllers Association union, said air traffic controllers braced for a tough day. "Indianapolis Center is one of the major facilities bearing the brunt of the extra workload today due to the Chicago Center situation," Church said.
O'Hare is a main hub for United Airlines and other major carriers, with flights headed to international destinations. When controllers stop flights scheduled to fly to O'Hare, it has the potential to trigger a line of falling air traffic dominoes that will ruin travel plans for countless would-be passengers.
Illustrating the point, the flight tracking website FlightRadar24.com showed no aircraft flying in an area stretching from eastern Iowa to central Michigan.
Smoke at FAA facility stopped flights in May
Friday's flight stoppages come four months after smoke at an FAA radar facility in Elgin, Illinois, prompted flight cancellations and delays at O'Hare and Midway.
In that May 13 incident, most flights in and out of O'Hare were delayed by an average of an hour or more, and more than 600 flights were canceled, the Chicago Department of Aviation said. Some 75 flights were canceled at Midway.
The smoke in that May incident was caused by a faulty motor in an air conditioning system, the FAA said at the time.
CNN's Mike Pearson and Amanda Watts contributed to this report.