In the months after Sept. 11, airport screeners confiscated record numbers of nail clippers and scissors. But nearly half the time, they failed to stop the guns, knives or simulated explosives carried past checkpoints by undercover investigators with the Transportation Department's inspector general. In fact, even as the Federal Aviation Administration (news - web sites) evacuated terminals and pulled passengers from more than 600 planes because of security breaches, a confidential memo obtained by USA TODAY shows investigators noticed no discernable improvements by screeners in the period from November through early February, when the tests were conducted. At screening checkpoints,...