(NewsNation) — Flight cancelations and delays are seemingly back under control but questions remain a day after a government computer system failure threw air travel across the U.S. into chaos.

As of 4 p.m. ET on Thursday. just more than 3,000 flights have been delayed within the U.S., and 140 flights have been canceled, according to flight-tracking website FlightAware.

The Biden administration called for an investigation into the outage and is now saying they’ve likely found the root cause.

The FAA released a statement saying, in part: “Our preliminary work has traced the outage to a damaged database file. At this time, there is no evidence of a cyber attack.”

Airports and the administration are working double-time to put Wednesday’s incident behind them.

U.S. Transportation Secretary Pete Buttigieg addressed the ongoing investigation in a radio interview.

“My focus now is understanding how this could have happened,” Buttigieg said. “This is a system that has already been in the process of going through modernization. There are a lot of aging systems at the FAA.”

Millions of passengers were stranded for hours after the first nationwide aviation ground stop in more than 20 years was ordered after a critical safety system that notifies pilots of potential hazards went dark.

The outage caused more than 1,300 flight cancelations and nearly 11,000 delays across the U.S.

The lack of a permanent FAA administrator has forced Buttigieg to assume a more public-facing role. Just two weeks ago, he scrutinized Southwest Airlines for their outdated technology, which caused a holiday travel crisis.

Republican Texas Sen. Ted Cruz took to social media to lambast the FAA over the incident.

“The FAA’s inability to keep an important safety system up and running is completely unacceptable and just the latest example of dysfunction within the Department of Transportation,” Cruz tweeted. “The administration needs to explain to Congress what happened.”

White House press secretary Karine Jean-Pierre defended Buttigieg.

“Does President Biden have confidence in Secretary Buttigieg? Yes,” she said.

But Canada’s aviation system was briefly hit with a similar outage hours after the U.S. announced their ground stop.

Canada’s system failure lasted only a few hours and didn’t delay any flights.

The country’s air navigation service provider released a statement on social media saying, “Nav Canada continues to investigate the cause of the outage; at this time, we do not believe it to be related to the (FAA) outage experienced earlier today.”

The FAA also said it is working to further pinpoint the causes of this issue to make sure this kind of disruption never happens again.