(CNN) — Officials are still trying to figure out exactly what led to the Federal Aviation Administration system outage on Wednesday but have traced it to a corrupt file, which was first reported by CNN.Another source familiar with the Federal Aviation Administration operation described exclusively to CNN on Wednesday how the outage played out.During this early morning process, the FAA told reporters that the system was "beginning to come back online," but said it would take time to resolve.Transportation Secretary Pete Buttigieg ordered an after-action review and also said there was "no direct evidence or indication" that the issue was a cyberattack.Top image: A traveler looks at a flight board listing delays and cancellations at Ronald Reagan Washington National Airport on January 11."