The router fault behind the nationwide US ground stop overloaded communications at 17 of the FAA's 22 en route centres, Reuters reports. It says the FAA ordered the nationwide stop because it could not identify a root cause.
Transportation Secretary Sean Duffy said on Saturday 14 November that the flood of connection attempts caused communication problems with aircraft and disrupted radar feeds, ABC7 reports. He said systems came back once the FAA isolated the contractor's work at the remote site, according to Bloomberg.
Reuters says the routers being replaced are about 25 years old. Duffy said they were supposed to be replaced in 2006.
Reuters also reports that the FAA spends $1bn a year to maintain its old copper-wire system. It says more than 20,000 flights have been disrupted since Friday.
Officials told Reuters there may have been problems with routers in both Arkansas and Texas, according to a Yahoo News live blog. This has not been confirmed.