Congress is examining the security risks to passenger planes from the so-called insider threat, terrorists who quietly get at airports so they can attack from within sensitive areas.
There has never been such an instance, but a security supervisor at Newark Liberty Airport is facing criminal charges that nearly 20 years ago he assumed the identity of a New York man who was later murdered.
The House Homeland Security Committee was conducting an oversight hearing Wednesday.
The acting inspector general, Charles Edwards, told lawmakers in prepared testimony that people who pose a threat can obtain government security badges for U.S. airports because the Transportation Security Administration inadequately investigates the backgrounds of badge applicants.
He said this includes missed signs they might be dangerous or confirming they were American citizens.