A survey of airline passengers found that more than 20 percent had knowingly or unknowingly smuggled prohibited items past Transportation Security Administration checkpoints onto the aircraft, including at least 6 percent who boarded the plane while unintentionally carrying prohibited knives or other bladed objects.

Less than 1 percent claimed that they discovered belatedly that they had mistakenly traveled with firearms, ammunition or explosives.

The survey of more than 1,000 people – which was conducted by a jet-chartering service Stratos Jet Charters Inc. – also found that younger travelers were more likely to flout the rules. Of the respondents who admitted knowingly trying to fly with something banned by the TSA, 19.7 percent were millennials, compared with less than 15 percent who were members of Generation X.

The most common items whisked past TSA agents on purpose were food and liquids. More than 3 percent admitted knowingly carrying bladed items past security, while 2.2 percent of female respondents and 3.7 percent of male respondents also acknowledged intentionally carrying prohibited drugs onto the aircraft.

The company said it surveyed travelers around the country to find out how many had accidentally brought contraband through airport security and how many had done so on purpose. It’s no surprise that the people most likely to haul contraband past security – knowingly or unknowingly – were those who fly the most.

As the company points out, however, the TSA guidelines are somewhat complicated and confusing. People are often uncertain of what liquids they can carry or how much of them. So it’s no surprise that the largest amount of stuff seized by the TSA happens to be forbidden liquids. For a time, people thought the TSA might be treating books as contraband.