Hundreds of flights to and from airports throughout a large swathe of the US, from New York to the Carolinas, have been delayed or cancelled by an air traffic problem which frayed passengers' tempers.
The Federal Aviation Administration blamed the delays on "technical issues" at an air traffic control centre in Leesburg, Virginia. The agency said the problem had been resolved at around 4pm local time yesterday and officials were working to lift any remaining orders to hold planes on the ground.
Delays began building at about 9.45am, according to FlightRadar24, a flight monitoring website. Flights bound for airports in the Washington area were some of the most affected, including Washington's Reagan National Airport and Dulles International, as well as Baltimore-Washington International Thurgood Marshall Airport and Charlotte-Douglas International Airport in North Carolina.
By mid-afternoon, 50 per cent of inbound flights and 42 per cent of outbound flights had been cancelled at Reagan National and delays were averaging about three hours, according to FlightRadar24.
In Baltimore, 58 per cent of inbound flights and 36 per cent of outbound flights had been cancelled and delays were averaging over an hour.
Flights leaving Newark Liberty International Airport in New Jersey and John F Kennedy and LaGuardia airports in New York that normally flight over the Washington region as they headed southwards were also affected, although the FAA had said it was trying to route the flights around the affected area.
FAA officials had no immediate estimate of how many flights were affected, but FlightRadar24 spokesman Ian Petchenik said it was certainly in the hundreds.
The agency said the snarl was the result of an "automation problem" at the Leesburg centre, which handles high-altitude air traffic for the affected region. The problem was not believed to be caused by any accident or hacking.
Information posted online by the FAA indicated there was a problem with the En Route Automation Modernisation computer system, also known as ERAM, at the Leesburg centre.
The FAA finished installing the troubled computer system in the last of 20 high-altitude traffic control centres earlier this year. The completion was years behind schedule.
"The FAA is continuing its root cause analysis to determine what caused the problem and is working closely with the airlines to minimise impacts to travellers," the agency said.