Flights across the United States have been affected by a technical glitch with a computer system in an unprecedented disruption, news reports said on Wednesday.

All flights in the US were grounded following the incident, NBC News reported, quoting a source.

All flights in the US were grounded following the incident, NBC News reported, quoting a source.

Flight tracking website FlightAware reported about 3,700 flights within, into or out of the United States had been delayed as of 7 am US Eastern Time.

An additional 100 flights were also cancelled.

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 and is working to restore a system that alerts pilots to hazards and changes to airport facilities and procedures that had stopped processing updated information.

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

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 were still viewable.