ALEXANDRIA — Holiday travelers could receive enhanced pat-downs at the hands of Transportation Security Administration agents in the next few days, but TSA failed to enforce a key foreign pilot screening process that could have prevented the Sept. 11 terrorist attacks.

For several months in 2010, TSA and Department of Defense contractor Mantech International Corp. failed to enforce the Alien Flight Student Program, which performs threat assessments and background checks on about 35,000 non-citizens learning to fly every year.