TSA’s multi-layered process to vet aviation workers for potential links to terrorism was generally effective. In addition to initially vetting every application for new credentials, TSA recurrently vetted aviation workers with access to secured areas of commercial airports every time the Consolidated Terrorist Watchlist was updated. However, our testing showed that TSA did not identify 73 individuals with terrorism-related category codes because TSA is not authorized to receive all terrorism-related information under current interagency watchlisting policy.