The TSA's list of prohibited items can be broken down into two categories: items that aren't allowed to be carried on board but may be checked with luggage, and items that are prohibited from being brought onto a plane altogether.
Among the items prohibited from carry-on baggage but allowed to be checked include many types of sharp objects including box cutters, knives and razor blades; sporting goods items such as baseball bats, pool cues and ski poles; firearms that are packed in a locked, hard-sided container and declared to airline employees when the passenger is checking in; and even many self defense items such as night sticks and stun guns.
The list of items the TSA prohibits altogether from air travel (even with checked baggage) includes many explosive materials such as fireworks, hand grenades, plastic explosives, gasoline, lighter fluid and even flammable paints.
The U.S. Transportation Security Administration (TSA) does not regulate the size of bags that can be carried onto an airplane by passengers. Instead, those rules are determined by the individual airlines. However, the TSA does regulate the types of items--particularly those that are potentially dangerous--that must be safely checked with baggage into the airplane's cargo bay.