India, Nov. 14 -- US Transportation Secretary Sean Duffy said a legacy air traffic control communications system became overloaded and began issuing faulty data, prompting a nationwide "ground stop" on Friday that led to more than 10,000 cancelled and delayed flights.

This comes after the Federal Aviation Administration (FAA) grounded all departing US flights on Friday for just the second time since the 9/11 attacks in 2001, citing "extraordinary circumstances" caused by communications problems at regional air traffic control centres.

The agency described the problem as "a temporary telecommunications outage" and said it was acting "out of an abundance of caution." The ground stop for US flights, which halted thousands of departures and...