Carrying all knives onto a plane, including small pocket knives, is prohibited, according to the Transportation Security Administration's list of prohibited items posted on its website. However, such knives are perfectly fine in checked bags, along with other sharp objects, such as scissors and even meat cleavers.
Carrying Swiss Army knives was permitted briefly in early 2013 in attempt to allow TSA agents to focus on more serious items that might sneak their way through security, according to an ABC news report. However, as William Saletan writes for Slate.com, the time period following the rule change was plagued with shootings, a couple of them in schools, and the anti-knife movement gained ground. As a result, the TSA decided to change its mind.