Guns and knives, along with box cutters like those used by the Sept. 11 hijackers, slipped past screeners in recent airport security tests by undercover agents. Two years after the terrorist attacks prompted tighter security at airports nationwide and the deployment of 50,000 government-paid screeners, congressional investigators found that the Transportation Security Administration has not stopped the flow of lethal weapons through checkpoints. The frequency and types of weapons remain classified. “You wouldn’t want to know. … It’s gruesome,” said Rep. John Mica, R-Fla., chairman of a House aviation panel. “We have a huge army (of screeners) that’s not working well.” Full Story