ATLANTA - Numerous flight delays caused by an electronic communication failure at a Federal Aviation Administration facility drew new criticism for an agency that has been scrutinized over air traffic controller staffing levels and inspection standards for its ground-based equipment.

The Northeast was hardest hit by the delays prompted Tuesday by a glitch at a Hampton, Ga., facility that processes flight plans for the eastern half of the U.S.

As of Wednesday morning, the FAA said that the situation around the country had returned to normal, with most delays from the malfunction being cleared up Tuesday night. But spokeswoman Diane Spitaliere said the investigation into what caused the problem is still ongoing, and she did not know when it would be completed.

"It usually takes a while to be quite honest," she said.

At one point, an FAA Web site that tracks airport status showed delays at some three dozen major airports across the country. The site advised passengers to "check your departure airport to see if your flight may be affected."

The FAA said the glitch appeared to have involved a software problem.

Sen. John McCain, the Republican presidential candidate, said the episode "once again highlights the need to reform and repair a broken system." His Democratic rival, Sen. Barack Obama, said "airline passengers are sick and tired of delays and cancellations." And the nonprofit Travel Industry Association called it "one there from Tuesday's episode. Bergen said officials at the Atlanta airport were entering flight data manually to try to speed things up.

Discount carrier AirTran Airways, which has its hub at the Atlanta airport, said in a statement that because of the suburban FAA center snafu it was at one point taking up to an hour for the FAA to get clearances to the towers for departures Tuesday. Delta Air Lines Inc., which has its main hub in Atlanta, said flights were processing for takeoff, but slowly.

The communication failure caused delays for departures and arrivals at Baltimore-Washington International Thurgood Marshall Airport, according to airport spokeswoman Cheryl Stewart. However, she did not have a number on delays.

The FAA at one point asked that no new flight plans be filed, Stewart said.

Phil Orlandella, a spokesman for Massport, which operates Boston's Logan International Airport, said there were significant delays there, but the situation eased up by Tuesday evening.

The National Airspace Data Interchange Network is a data communications system for air traffic controllers. It's used to distribute flight plans and allows controllers to know when planes are leaving, where they're going and other details.

Allen Kenitzer, a western regional spokesman for the FAA, said the Utah system could handle the extra load while workers tried to get the Atlanta area system back online, but it was expected to slow down air traffic.

"We're not going to let an unsafe condition exist. It's just going to be slower," Kenitzer said.