Steve Elson, who used to test checkpoint security for the Federal Aviation Administration, helped us with our tests.
"When the bag goes through the X-ray, there's a big black blob," says Elson. "They're impossible to miss and yet they just continually let it go."
Screeners could not clearly see what was in our carry-ons and should have searched them, because a weapon could have been hidden in or under the film bags.
But 70 percent of screeners failed to check or even detect the film bags. At the time, the Transportation Security Administration blamed a broken system. Congress ordered the federal government to take over all airport checkpoints by Nov. 19.
But with two months to go, of the seven airports we re-visited, Baltimore was the only one where federal employees screen all passengers. At the rest, private companies -- under federal supervision -- still handle some, if not all, of the screening. They are not government employees and have not received the same training.
The new head of the TSA, James Loy, says security has improved.
"It has changed dramatically for the better," says Loy. "I am very impressed with the diligence of the screeners that are in place today."
To determine if screening really has improved, CBS News went back to the same airports using the same kind of X-ray blocking film bags, and we got the same results. Once again, 70 percent of the time, those film bags went undetected or unopened.
In Los Angeles, screeners actually did worse. Last time, they found and checked our film bags 50 percent of the time. Last week, they missed all of them.
We'd also been detected 50 percent of the time at New York's LaGuardia. On this latest round, which Elson also helped us with, screeners failed every test.
"LaGuardia was a typical day," says Elson. "You go through and you think there's no way to miss this, and yet we just generally sailed right through the checkpoint."
In two incidents, screeners did find one film bag, but missed a second one that a CBS News producer was also carrying.
"They had the idea, but they didn't carry it through to completion," says Elson. "Therefore, they failed."
Screeners at Atlanta and Washington's Reagan National didn't check any of our film bags six months ago, and again they missed all of them this time.
None of the screeners at New York's Kennedy airport stopped us last time. That happened again in four out of five tests.
There were some success stories. Screeners in Ft. Lauderdale stopped us and checked the film bags six months ago and did everything right again last week.
In Baltimore, all screeners are federal employees. Earlier this year, the film bags went undetected every time. Last week, our film bags were searched every time.
"This is the first time they've ever, on any of the things we've done, (that) they've ever opened the bag and done it successfully," says Elson. "And they did it very well today.
"I hope that's the wave of the future."
But a year after Sept. 11, Elson is still worried.
"They're missing all kinds of things," says Elson. "That's the frightening part."
Things like guns.
A checkpoint supervisor at Atlanta's airport was fired last week after a woman boarded a plane with a loaded weapon and extra ammunition. She was caught at another airport, by the new layer of pre-boarding screening in gate areas, a security requirement the government may eliminate for passenger convenience.