A computer glitch has caused widespread delays and the cancellations of flights in the United States, the Federal Aviation Administration (FAA) has said.

FAA officials said the glitch, which lasted for five hours on Thursday, forced airlines to enter their flight plans manually.

But it said there were no safety issues arising from the problem, which was fixed shortly afterward.

The problem occurred in the Atlanta-based computer system that provides data about flight plans, the Reuters news agency quoted Arlene Salac, an FAA spokeswoman, as saying.

"There are not any safety concerns or safety issues," she said.

Flights cancelled

Doug Church, a spokesman for the National Air Traffic Controllers Union, said controllers were still entering flight plans manually in some places even after the glitch was fixed, the Associated Press news agency reported.

New York City's John F Kennedy International Airport was operating at 40 to 50 per cent efficiency because of the glitch.

AirTran Airways said 38 flights were cancelled and dozens more were delayed nationwide because of the problem.

Delta Air Lines was also experiencing flight delays and cancellations, a spokeswoman said.

The delays were made worse by inclement weather in the Northeast, with airports in the Chicago, Washington, DC, and New York metropolitan areas reporting disruptions.