TSA says peanut butter is classified as a liquid, sparking debate

The Transportation Safety Administration sparked a debate about the viscosity of peanut butter this month when they called it a liquid. Because the TSA considers the nut spread a liquid, plane passengers must limit the amount they bring in their carry-ons.

Like all other liquids, passengers are limited to 3.4 oz or less of peanut butter in their carry-on bag, but can also put the snack in their checked baggage.

The TSA tweeted about the peanut butter rule on March 21, joking that "you may not be nuts about it." They also shared the definition of a liquid, which "has no definite shape and takes a shape dictated by its container." 

Many Twitter users tried to poke holes in the TSA's logic. "If peanut butter is considered a liquid, then why is it sold by weight, and not volume? Also, does this same rule apply to chunky peanut butter?" one Twitter users replied.

One person shared images of cats fitting the shape of various containers – arguing they could therefore be defined as liquids.

One person said they were affected by the rule and had to "surrender a big jar of JIF once." 

Another person said that peanut butter could be considered a "non-Newtonian fluid," meaning it doesn't follow Isaac Newton's original law of viscosity. According to the American Chemical Society, the viscosity — how easily it flows — of a non-Newtonian fluid is affected by a stress other than temperature, such as squeezing, shaking or stirring. That means sometimes, a non-Newtonian liquid can behave more like a solid.

Another Twitter asked if the rules changed if the peanut butter was on a sandwich. "Solid foods, including peanut butter and jelly sandwiches, are allowed in carry-on bags with no quantity limitations or packing requirements," the TSA Twitter account replied.

The TSA's social media accounts are known for making puns while simultaneously sharing travel information. In other recent tweets, they shared information about bringing different types of food through airport security.

"Traveling with your favorite chips and dip? You don't want it to become all chips and no dip. So be sure your creamy sauces are 3.4oz or less in carry-on. In queso you're wondering, all your travel-size liquids need to fit in a single quart-size bag," one tweet reads.

"Travel plans are no artijoke. So here's some light hearted news! Canned artichoke hearts are good to go in checked bags. They can even fly in a carry on if their liquid content is 3.4oz or less," another tweet reads. 

The TSA requires "any item you can spread, smear, spray or spill" to be 3.4 oz or less if in a carry-on, and all the liquids a passenger is traveling with must fit in a quart-size bag. 

CBS News reached out to the TSA for more information and comment on the peanut butter rule and is awaiting response.