The Federal Aviation Administration (FAA) has lifted a nationwide ground stop that was declared Friday afternoon, delaying or canceling more than 11,000 US flights, according to aviation tracker FlightAware , and throwing airports into sudden chaos.

The FAA confirmed the airspace was open in an advisory on its website . “So at 8.15 tonight, Eastern Time, we’ve opened up the airspace,” Sean Duffy, the US transportation secretary, said. “But it’s going to take us some time to unwind what’s happened this afternoon .”

Duffy said that the federal government has “identified the problem” that brought down the US air traffic control system on Friday and the system “is operational right now”.

The White House briefing Friday evening with Duffy and Markwayne Mullin, the homeland security secretary, quickly turned into a plea for funding from Congress to “fully fund a full build of a brand new air traffic control system”.

“What we have is an incredibly old air traffic control system,” Duffy said.…