WASHINGTON — Hundreds of commercial airline flights were delayed across the Eastern half of the United States on Tuesday in what the Federal Aviation Administration said was an unprecedented glitch in the federal computer system that processes flight plans.
While the breakdown caused chaos at big-city airports — including Washington, New York, Atlanta and Boston — passengers were never in danger, FAA officials stressed. The agency was close to regaining control of the system by late afternoon East Coast time.
The problem began about 1 p.m. EDT with a computer breakdown at the FAA's primary flight plan-processing system in Atlanta, FAA officials said in a hastily arranged conference call. A backup system at Salt Lake City went into operation but became overloaded, compounding the delays.
Airplanes were unable to take off because their flights plans hadn't been processed, creating ground congestion that delayed incoming flights. At one point, at least 40 flights backed up at Atlanta's Hartsfield-Jackson International Airport. Others hit with heavy delays included O'Hare International and Midway International airports at Chicago, Washington Dulles International and Ronald Reagan Washington National airports in Washington, D.C., and Baltimore/Washington International Thurgood Marshall Airport just south of Baltimore.
The slowdown could result in some flight cancellations or delays Wednesday morning as the major airlines work to clear the backlog. American Airlines spokeswoman Andrea Huguely advised passengers to check their flight status before leaving for the airport.
FAA officials said tower operators remained in contact with flight crews and kept planes safely separated.
"It's not a safety issue," FAA spokeswoman Tammy Jones said.
The breakdown of the automated system, called NADIN, was the first of its kind and baffled FAA officials, who were conducting a technical investigation to determine the cause.
"We've just never seen it fail in this manner," said Hank Krakowski, the chief operating officer for the FAA's Air Traffic Organization. "We're going to have to do some forensics. These are very complicated systems."
Krakowski said the problem affected airports east and north of Dallas-Fort Worth, hitting East Coast airports particularly hard. Without automated processing, officials were forced to punch in flight plans manually, further worsening the delays.
The problem appeared to be abating by 5 p.m. EDT, although Atlanta and Baltimore still were experiencing some delays.
FAA officials said hundreds of flights were delayed throughout the afternoon, but they were unable to point the exact number. At least 5,000 flights were in the system, Krakowski said, but many were airborne and thus not affected.
(Trebor Banstetter of the Fort Worth Star-Telegram contributed to this article from Fort Worth, Texas.)