The Federal Aviation Administration said normal operations were "resuming gradually" after ordering a nationwide pause on all domestic departures until 9 a.m. on Wednesday morning following a computer failure that has impacted flights around the country.

"The ground stop has been lifted," officials said at about 8:50 a.m. ET. "We continue to look into the cause of the initial problem"

The affected Notice To all Air Missions, or NOTAM, system is responsible for sending out flight hazards and real time restrictions to pilots, administration officials said earlier.

"The FAA is still working to fully restore the Notice to Air Missions system following an outage," said the FAA announcing the temporary grounding of all planes nationwide. "The FAA has ordered airlines to pause all domestic departures until 9 a.m. Eastern Time to allow the agency to validate the integrity of flight and safety information."

A senior official briefed on the FAA computer problems tells ABC News the software issue developed late last night and led to a “cascading” series of IT failures culminating in this morning’s disruption. As has been reported, the disruption is confined to the commercial side of aviation.

Engineers are feverishly working to fix the problems and, separately, identify precisely what happened. As of now, the assessment is the failures are the result of a “glitch” and not something intentional. All possibilities are being looked at to ensure that the FAA systems were not breached.

Notably, the FAA system that failed is overdue for replacement.

The official compared the current outage to the crisis that crippled Southwest Airlines during the holidays: antiquated software overdue for replacement inside a critical IT network. If one thing goes down, the system can become paralyzed.