At Newark Airport Friday, a reminder of items not allowed on board planes: solvents, household cleaners, and, yes, chainsaws.
Yet, as NBC News exclusively reported on Thursday, four and a half years after 9/11, government investigators got materials for homemade bombs through security at all 21 airports they tested.
“I find it very alarming,” says traveler Jewel Brooks in Mississippi, “because they assured us that they were going to take all the necessary measures.”
“It scares me,” agrees Dallas traveler Cindy Bullock. “It makes me mad that the government hasn't done something about it.”
Rep. Ed Markey, D-Mass., says this proves that the Transportation Security Administration has not improved safety nearly enough.
“TSA is way behind,” he says. “TSA has put a beware-of-dogs sign on the lawn, but not purchased a guard dog.”
Analysts say detecting materials for homemade bombs is not easy because the ingredients themselves aren't dangerous — or explosive — until combined with other materials.
TSA says it now considers explosives the No. 1 threat. And Friday, TSA Assistant Secretary Kip Hawley argued that even though bomb materials got through the screeners, there are many other layers of security to keep terrorists with bombs off planes. Among them: watch lists and behavioral analysis.
“Any one piece can be beatable,” Hawley says, “but it's the combination of many put together that we believe is very secure.”
TSA says, so far, about half of its screeners have been trained to detect homemade bombs. But Peter Winch, of the American Federation of Government Employees — the TSA screeners’ union — complains that's not enough.
“TSA could give them additional equipment and additional training to stop this threat,” Winch says.
TSA argues that it needs more money to improve technology and hire more officers. Still, most analysts believe that a well-trained screener is the best defense against the very real threat of homemade bombs.
Lisa Myers is NBC’s senior investigative correspondent