U.S. Sen. Dick Durbin said Sunday that he will seek an investigation into how a contract employee was able to sabotage a regional control center and bring Chicago's two international airports to a halt.

The Illinois Democrat told The Associated Press that he will ask inspectors general at the U.S. Department of Transportation and the Federal Aviation Administration to investigate whether there was a security breach when the employee entered the building early Friday with a suitcase without causing suspicion. He then started a fire in the basement telecommunications room before attempting to commit suicide by slashing his throat.

Brian Howard, 36, of Naperville, who had access to the control center in suburban Aurora via a swipe card, entered around 5 a.m. Friday, and about 30 minutes later posted a suicide note on Facebook, according to a federal criminal complaint.

Minutes later, someone at the facility called 911 to report the fire. A relative who saw the Facebook post also alerted authorities. Paramedics followed a trail of blood past a gas can, two knives and a lighter and found the suspect slashing his throat, the complaint said. He also had cuts to his arms.

Durbin said he is grateful that the FAA was able to get all planes on the ground safely. He said FAA Administrator Michael Huerta told him that 23 of 29 computer racks were damaged, and the FAA said Sunday that it decided to replace the entire central communications network at the center.

"Thank God nobody lost their lives, but it could have happened in this circumstance," Durbin said.

Sen. Mark Kirk said Saturday that he wanted an immediate review of the FAA screening process at the site, and a report within 30 days outlining future changes.

On Sunday, 550 flights were canceled at O'Hare and 50 at Midway. At the height of the travel misery Friday, more than 2,000 flights in and out of the airports were canceled, disrupting travel nationwide.

FAA spokeswoman Elizabeth Cory said improvements were expected on Monday, although the system would not be fully functional.

The facility in Aurora, about 40 miles west of downtown Chicago, handles planes cruising at high altitudes through the air space as well as those just beginning to approach or completing a departure from airports in the Chicago area. Its responsibilities have been transferred to centers in Cleveland, Indianapolis, Kansas City and Minneapolis.

Cory said the FAA has been able to increase air traffic and reduce delays by improving direct communication between the centers now handling Chicago's air traffic, and by developing new ways to automatically file and transfer airline flight plan information.

The FAA said it conducts employee background checks on contract workers like Howard who have access to FAA facilities, information or equipment. Contract employees, like other staff at the Aurora facility, also must have their identification inspected by a perimeter guard and must swipe their cards to gain access to the building.

Howard worked at the facility for eight years and was involved with the facility's communications systems. He was recently told he was being transferred to Hawaii.

Durbin said it's possible that Howard's suitcase did not cause concern because security believed he was retrieving personal belongings in preparation for his move.

Howard was charged with destruction of aircraft or aircraft facilities, a felony. If convicted, he could be sentenced to up to 20 years in prison.