If you are traveling today, you may want to check with your airline.

Thousands of flights into and out of Chicago's two airports have been delayed or canceled since a fire damaged a key Chicago air traffic control center Friday, creating flight problems that rippled across the nation.

Aviation authorities say it will take at least two weeks to get the center back to normal.

One airport affected, O'Hare International, is the world's second-busiest airport.

Long lines of stranded passengers have been clogging Chicago airports all weekend.

O'Hare was operating at 60% of its capacity Monday, according to the Chicago Department of Aviation, while Midway International Airport was at 75%. As of Monday morning, at least 300 flights had been canceled at O'Hare.

The FAA hopes to have the center in Aurora, Illinois, repaired and returned to full service by October 13, the agency said Sunday.

Other control centers have handled many of the Chicago flights while repairs are made.

Police say Friday's blaze was set intentionally by Brian Howard, a contract employee at the facility, before he apparently attempted to kill himself.

According to an affidavit, first responders found smoke when they arrived in the basement of the control center after a 911 call about 5:40 a.m. Friday.

They also found blood on the floor. They followed the trail and found two knives and a lighter and then Howard himself, who was in the process of cutting his throat, according to the affidavit.

The paramedics took a knife from him and began to treat Howard, who told them to leave him alone. Howard was taken to a hospital in Aurora.

Howard remained hospitalized Monday, according to Randall Samborn, spokesman for the U.S. Attorney's Office in Chicago.

He's charged with one count of destruction of aircraft or aircraft facilities, a felony that could bring a 20-year prison sentence. No court date has been set.

Howard, 36, had worked at the center for eight years but was facing a transfer to Hawaii, according to an affidavit filed in U.S. district court in Illinois, obtained by CNN affiliate WLS.

The affidavit quoted a Facebook post's of Howard's: "Take a hard look at the mirror, I have. And this is why I am about to take out... and my life... I am sorry. Leaving you with a big mess. Do your best to move on quickly from me please. Feel like I give a shit for the first time in a long time again... but not for too long (haha!) So I'm gonna smoke this blunt and move on, take care everyone."

The FAA will launch an internal review of security protocols at its facilities, its administrator said Monday.

"If we need to make changes as a result of what happened on Friday to improve the system, we will not hesitate to do so," Michael Huerta said.

"We need to be looking at everything ... from the people that we employ through our contractors, all the way through all the processes that we use -- how they have access to our facilities and what kind of monitoring takes place within those facilities. That's all on the table," he said.

Huerta told CNN that background checks on Howard had not identified any potential problems, and so he wants investigators to look into that vetting process too.

"Are there things that we need to do differently? Immediately, it's more eyes, more resources, and more frequent check-ins with facilities, but over the long term, if there are things that we identify that we should change, we're certainly going to change them," the administrator said.

Sen. Dick Durbin of Illinois is calling for an investigation into whether security was breached. The suspect was able to enter the facility with a black suitcase without raising any red flags, officials have said.

CNN aviation analyst Mary Schiavo said the FAA has to take a second look at who has access to critical facilities.

"You have to make sure you have a system in place to evaluate your contract employees, because remember, the Federal Aviation Administration ... huge percent of their employees are contract employees," she said. Most of the air traffic controllers are FAA employees, she added.

After the fire, air traffic controllers initially had to transfer flight data manually rather than by computer, said Doug Church, spokesman for the National Air Traffic Controllers Association.

Church said the fire damaged the telecom line that transfers flight plans from the airlines to the O'Hare control tower and then to the Aurora control center.

Airlines had to fax flight plans to the control tower, he said. Because so much information had to be manually transferred, two controllers were needed for each position.

The effects of the fire were immediate.

O'Hare International is a hub for United Airlines and other major carriers. When controllers stop flights scheduled to land or depart from there, it has the potential to trigger a line of falling air-traffic dominoes that will ruin travel plans for countless would-be passengers.

The FAA says it's bringing in extra technicians to replace the damaged communications network in the building, officially called the Chicago En Route Center.

"Teams will be working around the clock to install equipment, run cable and restore network connections at the facility," the FAA said.

The FAA said over the weekend that it was managing the air traffic into 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."

(CNN)