Yes, according to the TSA (Transportation Security Administration), peanut butter is classified as a liquid or "gel" because it can be spread, smeared, or poured. Under the 3-1-1 rule, this means any container of peanut butter in your carry-on luggage must be 3.4 ounces (100ml) or less and must fit inside your single quart-sized clear bag. If you have a standard-sized jar of peanut butter, it will be confiscated at the security checkpoint. However, there is a loophole: if the peanut butter is already spread onto a sandwich (e.g., a PB&J), it is considered a solid food item and can be brought through security in any quantity. For larger jars, your only option is to pack them in your checked baggage where there are no volume restrictions.