The FAA said the issue occurred while personnel were working "to correct synchronization between the live primary database and a backup database." The FAA said it "has so far found no evidence of a cyber-attack or malicious intent."

FAA acting Administrator Billy Nolen plans to hold a virtual briefing Friday for lawmakers and staff, who have sought details of what went wrong with a pilot messaging database that led to the first nationwide grounding of departing flights since the Sept. 11, 2001, attacks.