Transportation Security Administration administrator Kip Hawley was grilled before a Congressional committee on Wednesday after covert federal investigators smuggled the components of liquid-based bombs past screeners in 19 airports nationwide in secret tests earlier this year. During the hearing, spirits heated up as witnesses tried to talk over one another.

Rep. Henry A. Waxman (D-Beverly Hills) said that "the situation is unacceptable. There are too many vulnerabilities and we've got to fix them. It's disappointing that after all the years we've had TSA in place and all the money, billions of dollars, that we have put into the problem, it's still not fixed."

At issue was also an apparent attempt to tip off security screeners of a specific secret test. On April 28, 2006, an e-mail from a TSA official who oversees security operations warned that "several airport authorities and airport police departments have recently received informal notice" of security testing being carried out by the Department of Transportation and the Federal Aviation Administration.

The e-mail also gave details about the testing, such as that a couple will attempt to breach security, of which the woman was to be white but to have "an oriental woman's picture" on her identification card.

"Relying solely on security at the checkpoint or focusing all of our resources to defeat one threat is counterproductive and detracts from our overall mission," Hawley said in written testimony. He pointed out that TSA's defenses are multilayered. They allegedly include measures such as canine teams in airports, hardened cockpit doors, special self-defense training for airline crews and armed pilots.

"If screeners still fail tests that they know are being conducted, heaven help us when Al Qaeda next probes for weaknesses," Clark Kent Ervin, a former inspector general for the Department of Homeland Security, said.

Experts have pointed out that TSA critics might have unrealistic expectations, as any security system will have weaknesses. In particular, screening is meant to be largely a deterrent to take amateurs off the field and deter the pros. It is definitely not infallible.

Last month, TSA began testing a new type of walk-through security machine, which uses a technology called active millimeter wave, at Phoenix Sky Harbor Airport (PHX).

According to TSA, the new technology, which is also less invasive than X-ray technology used in TSA’s first pilot program, can detect weapons, explosives and other threat items concealed under layers of clothing without physical contact.