Morrisville, N.C. — Flight delays were unwinding across the country Thursday afternoon after an early morning software glitch prompted widespread problems in domestic air travel.

At Raleigh-Durham International Airport, the director declared all systems go just after 2 p.m.

The FAA system that plans flights went offline at about 5 a.m. The glitch was fixed by 10 a.m. but caused widespread flight cancellations and delays as air traffic controllers moved to a manual system of departures and arrivals.

Airplane dispatchers had to send plans to controllers, who entered them into computers by hand.

"It's slowing everything down," FAA spokesman Paul Takemoto said.

At noon., the FAA reported departure delays of less than 15 minutes at RDU. Charlotte had departure delays between 15 and 30 minutes.

General departure delays of over an hour developed in northeastern airports from Washington, D.C., north to New York City. Controllers in the congested New York City air space were putting about 20 miles between planes in the air instead of the typical 8 miles, to create extra safety buffers.

Passengers were asked Thursday afternoon to continue checking the status of their flights online before going to airports.

Flight plans are collected by the FAA for traffic nationwide at two centers, one in Salt Lake City and one in Atlanta.

Victor Santore, the National Air Traffic Controllers Union southern region vice president, said he began getting e-mail messages from air traffic controllers around 7 a.m. EST Thursday that the Atlanta-area computers had stopped processing flight plans.

Santore said some controllers were pulled away from their normal duties talking to airplanes or pulled off breaks to help enter the flight plans.

"When something crazy like this happens, we'll pull everybody onto the floor," Santore said. "Every airport at some point some will be affected ... (The delays) are going to ripple through the entire system."

In August 2008, a software malfunction delayed hundreds of flights around the country.

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

The FAA said at that time the source of the computer software malfunction was a "packet switch" that "failed due to a database mismatch."