The FAA also said there were delays at New York’s LaGuardia and John F. Kennedy worldwide airports.

The FAA said it is continuing to investigate the root cause of the problem, and was working closely with the airlines to minimize impacts to travelers.

The tie-up at the major East Coast hub airports is triggering further delays across the country.

Disgruntled passengers said their flights were re-routed or there were dozens of planes ahead of theirs in line to take-off.

Some flights are still arriving at RDU, while others were diverted.

At Washington’s Reagan National Airport, half the flights have been delayed, and half were canceled.

The FAA said it was working with carriers to resume normal service and that the problem “has nothing to do with an accident or hacking”, Reuters reported.

The FAA did not say how many flights have been affected by the issue.

Two airports serving the Washington region were particularly hard-hit, with dozens of outbound flights canceled or delayed.

(AP Photo/Jacquelyn Martin). People ask questions at an information kiosk at Washington’s Reagan National Airport after technical issues at a Federal Aviation Administration caused delays and cancellations on Saturday, August 15, 2015.

Spokeswoman Jessica Wharton told us so far one United Airways flight has been cancelled and one Delta flight has been delayed.

The FAA Air Traffic Control System Command Center website lists a power failure at the Washington Air Route Traffic Control Center (ZDC ARTCC) as the cause of this. Then we got on the plane and were told the radar wasn’t available.

Some delays were as long as 2 hours, 45 minutes, officials said.