In three series of covert tests in March, May, and June of this year, undercover GAO operatives--posing as ordinary passengers--smuggled improvised explosive devices (IEDs) and one improvised incendiary device (IID) through security checkpoints. The bomb parts were real. The bomb parts were also commercially available, in some cases available over the Internet, for under $150. The 19 airports tested are not named in the congressional report by GAO Managing Director for Forensic Audits and Special Investigations Gregory Kutz--that's considered classified.

But--for those Thanksgiving celebrants routed through O'Hare, LAX, or JFK--it's a safe bet that a good chunk of the test sites were our larger hubs. We'd be idiots not to test them. In classic Red Team/Blue Team wargaming (which the GAO would have employed in selecting airports), the discerning counterterrorist would pick high-profile targets that al-Qaeda suicide bombers and their managers would desire for their characteristic tactical gains, namely, maximum American death and maximum PR value.

Dulles, say. Or Newark. Or Logan. To name the three where al-Qaeda operatives have struck so painfully before.

The GAO is the investigative arm of Congress, beholden to no cabinet-level political appointee, no White House "security" czar, no political party. The office decided to look at the TSA's bomb-detection capabilities as a result of August 2006's busted peroxide-bomb plot in London and the changing of screening rules for liquids. But the GAO operatives did not just smuggle liquids. They smuggled detonators and other bomb parts "concealed in their carry-on luggage and on their persons."

Prior to 9/11, we had highly professional, aggressive "Red" teams of undercover bomb-smugglers within the Federal Aviation Administration, but these teams were dismantled after 9/11 and the quality-control function of counterterror was moved inside the Department of Homeland Security. To be fair, the undercover TSA operatives test the TSA's screeners aggressively, to the tune of 2,500 tests per day, the agency spokesman says. But in the six years since the federalization of bomb screening, the "testers" have been responsible to the same Cabinet secretary as the TSA screeners being tested. Even high school football teams have separate offensive and defensive coordinators. It's just plain old good, tough training strategy.

The silver lining is that it's almost always good to know, objectively, how badly you're performing. So, at this moment, in addition to those distilleries providing us with liquid preflight bravery--double shot for a dollar extra, sir?--the American air passenger's best friend in counterterror practice may not be the TSA testers of the TSA screeners, but instead, the Forensic Audits and Special Investigations  unit of the GAO.