WASHINGTON (NewsNation) —  A Federal Aviation Administration (FAA) system failure on Wednesday caused the first aviation ground stop in over 20 years, something that hadn’t been seen since Sept. 11, 2001.

Now, the Biden administration said its top priority is figuring out exactly what happened to cause the hours-long pause.

“What you saw happen today was out of an abundance of caution,” White House Press Secretary Karine Jeane-Pierre said. “The safety of Americans is a priority.”

NewsNation learned that the FAA pilot safety communication system, otherwise known as NOTAM, went down when a corrupt file was discovered.

The FAA tried to reboot the system before the outage but was unable to resolve the issue before causing massive travel delays and cancellations throughout the country.

In its latest statement, the FAA said it is still “working diligently to further pinpoint the causes of the issue and take all needed steps to prevent this kind of disruption from happening again.”

The ground stop resulted in over 10,000 flight delays and more than 1,300 flight cancellations on Wednesday, but travel experts told NewsNation that it could take days for flight schedules to get back on track.

President Joe Biden ordered an investigation into the outage as Transportation Secretary Pete Buttigieg faces mounting pressure amid other transportation meltdowns.

Former Vice President Mike Pence said he was one of the passengers held at the Indianapolis airport, waiting to come to Washington, D.C. for the day. He called on the Biden administration and the Department of Transportation to give Americans answers and demand that airlines have the necessary technology.

“To my knowledge, this was the first national ground stop since 9/11 and the American people deserve to know why it took place, what happened and also what’s being done to ensure that we have the redundancy in the system to make sure this never happens again,” Pence told The Hill.

Republican U.S. Rep. Pat Fallon of Texas said they want to rule out any kind of cyberattack first. If this was a software glitch, he said more firewalls are needed to ensure fail-safe systems are in place so this doesn’t happen again.

“We need to know, we need to look into it, and ensure we do our due diligence to find out what the cause was,” he said. “We’re going to find out what the glitch was. We’re going to tell the American people what the glitch was and what we’re going to do to fix it.”

This is just the latest headache for travelers in the U.S. who faced flight cancellations over the holidays amid winter storms and a breakdown with staffing technology at Southwest Airlines. 

The FAA has been without a permanent administrator since March 31. Biden’s pick to head the agency, Denver International Airport Chief Executive Phil Washington, has not yet faced a hearing by the Senate Commerce Committee.

Washington has faced criticism from Republicans after he was named in a search warrant tying him to corruption allegations at the Los Angeles County Metropolitan Transportation Authority.

Meanwhile, FAA authorization is set to expire Sept. 30. Lawmakers have routinely extended the FAA legal authority to operate before reaching an agreement on authorization, but this outage may put pressure on Congress to take action.

The Associated Press and Reuters contributed to this report.