Washington/IBNS: After over 5,400 United States domestic flights were halted or delayed over a technical glitch, air traffic services resumed in the country on Wednesday evening (India time), the US Federal Aviation Administration (FAA) said in a statement.

All flights in the US were grounded following a technical glitch with a computer system in an unprecedented disruption.

Flight tracking website FlightAware reported about 5,400 flights within, into or out of the United States had been delayed till 7 am US Eastern Time.

An additional 100 flights were also cancelled.

The US Federal Aviation Administration (FAA) said normal air traffic operations are resuming gradually across the country.

It had earlier asked airlines to pause all domestic departures until 9 am US Eastern Time while they were working to restore a system that alerts pilots to hazards and changes to airport facilities and procedures that had stopped processing updated information.

Following the direction from the FAA, American Air tweeted: "The Federal Aviation Administration (FAA) is experiencing a nationwide system outage that affects all airlines. We're closely monitoring the situation and working with the FAA to minimize customer disruptions."

In an advisory, the civil aviation regulator said its NOTAM (Notice to Air Missions) system had "failed".

There was no immediate estimate for when it would be back, the website showed, though NOTAMs issued before the outage was still viewable.

United Airlines also said they temporarily delayed domestic flights until they heard more from the FAA.