The Federal Aviation Administration (FAA) said on Thursday a preliminary review found that contract personnel "unintentionally deleted files" disrupting a key computer system and prompting a nationwide groundstop on Jan. 11 that disrupted more than 11,000 flights.<p>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."