"If by some fluke your flight was targeted by terrorists right now, chances are they could do whatever they wanted to do," said Dzakovic, a current member of the government's elite Red Team, which covertly tests airport security.
Dzakovic routinely smuggled weapons and fake bombs past security checkpoints, reports CBS News Correspondent Vince Gonzales.
"We could breach security 80 to 90 percent of the time with very little problem before Sept. 11," Dzakovic said. And today? "I don't think we'd have that much more of a problem."
Government officials, however, insist security is tighter now.
So CBS News went undercover through checkpoints at eight major airports across the country to find out who's right.
We placed lead-lined film bags in carry-on luggage to show how dangerous objects might be smuggled onto planes. The bags, routinely used by travelers to protect film, can block x-rays from security scanners, even the latest machines.
The film bags should be checked because the only way for screeners to know for sure there's not a weapon or bomb inside is to open them. Which is why our test results were so disturbing. About 70 percent of the time, no one checked our film bags.
We easily got through JFK, Atlanta and Washington-Reagan airports. We went through Baltimore three times, twice on the day after a Justice Department high security alert.
In St. Louis, Los Angeles and New York's La Guardia, we got through once and were stopped once at each airport. In Fort Lauderdale, screeners correctly emptied the bag. At La Guardia, a supervisor explained why she searched it.
"We can't see through it," she said. "So we need to check it."
But twenty minutes later, at the same checkpoint, another screener let us through without inspection.
Click here for more on airport security.
"They didn't know what you were carrying. There could be anything in there, a weapon, a gun, a grenade," said Steve Elson, a former FAA Red Team leader who helped with our tests.
"To the American public, it appears that a lot is being done," said Elson. "But in fact it really isn't. And the very simple and more dangerous items are getting through, as we've seen during our time at the airport.
Dzakovic says inspectors have reported major security vulnerabilities and inadequate training of screeners for years, but he claims FAA officials ignored the problems.
"It was a disaster waiting to happen, and myself and other individuals desperately tried to have this stuff fixed before Sept. 11," he sid. "And absolutely nobody paid any attention."
The Department of Transportation wouldn't comment on Dzakovic's allegations, but it has been ordered to investigate. When told our film bags went unchecked nine of 13 times, officials acknowledged the current system has "inadequacies," but insisted airport security will improve "once the federal government assumes full oversight."
Rep. Jim Oberstar, D-Minn., one of the foremost aviation security experts in Congress, was disappointed by our test results.
"It shouldn't have been tolerated then and it cannot be tolerated now," said Oberstar. "It's exactly this kind of black hole in the system that has to be exposed and corrected."
Officials insist corrections are coming now that the new Transportation Security Administration has taken over from the FAA. And as we found, even six months after Sept. 11, there's still plenty of room for improvement.