Thousands of US flights cancelled or delayed as disruptions persist through Monday  

WASHINGTON — Thousands of flights across the United States were cancelled or delayed on Sunday as the nation’s aviation network struggled to recover from a technical failure that triggered an exceptionally rare nationwide ground stop, exposing the vulnerability of the country’s air-traffic control system and leaving widespread disruption in its wake. Secretary of Transportation Sean Duffy said normal operations may not be restored until Monday. “We have airplanes and crews that are out of position, so it takes a little bit of time,” he said. More than 5,000 flights were delayed and 2,000 cancelled on Sunday. US President Donald Trump urged Congress on Sunday to approve more money to modernize the air-traffic control system. The grounding of all aircraft scheduled to depart the US on Friday caused chaos at airports across the country. More than 3,500 airplanes were in the air when the FAA announced that flights would be grounded until further notice. Some were diverted to other airports and others flew on to their destinations. In the aftermath, 8,500 flights were delayed and another 8,000 cancelled, according to FlightAware. The stoppage left passengers stuck inside planes on the tarmac, unable to take off or to return to their gates. Others were stranded in airports, sleeping on the floor and desperately trying to get in touch with their airline. The ground stop also had a knock-on effect on schedules around the world, with some flights out of the UK and Europe cancelled. The ground stop was lifted after about four and a half hours, but the impacts continued over the weekend. On Saturday, airlines cancelled more than 5,900 flights and more than 7,000 others were delayed. Investigators are still working to determine the root cause and who is at fault, but Duffy said the administration decided to ground flights after failures in a key system that allows air traffic controllers and pilots to communicate. The transport secretary said a computer router installed as part of an upgrade from copper wire to fibre started sending out faulty signals. He said on Sunday that the router – a piece of equipment which directs traffic across the network – was installed in El Dorado, Arkansas, and “flooded our network”.