Especially in the United States, there are heavy restrictions on the types of items permitted on commercial aircraft. All airlines maintain a list of prohibited items in addition to the national list, and if you are uncertain about any item, you should contact the airline you are using, along with any airlines you are making connections on. Be aware that some regional airports have tighter security surrounding prohibited items than others as well. The most important thing to think about when questioning whether an item is prohibited or not is its potential use as a weapon: if it looks dangerous to you, it is probably not allowed.

The most obvious category of prohibited items is, of course, weapons. Explosives of any form are banned from the cabin of commercial aircraft along with fire arms, knives, other bladed weapons, brass knuckles, rope, flares, and all martial arts weapons. Tools and sporting equipment which could be used as weapons such as axes, baseball bats, hockey sticks, ice skates, and any sort of sticks or poles are also banned. In addition, chemicals which could cause physical damage, health problems, or explosions are prohibited: examples include mace, pepper spray, tear gas, and bleach. Be aware that items which closely resemble prohibited items are also banned: replicas of weapons, for examples.

Concerns about explosives have also led to bans on gels, liquids, and other substances which could potentially contain explosives. Exceptions to these prohibited items include bottled breast milk if you are traveling with a child, although the nursing mother may be asked to drink it in front of security personnel, along with liquids in amounts less than three ounces (88 milliliters) which are kept in clear containers. Aerosols such as spray paint are also prohibited items, and asthma sufferers may want to consider bringing sealed inhalers with a doctor's note through security to avoid difficulties. Compressed gases are also banned.

Most personal care items are permitted, as long as they agree with the above specifications. Be aware that any gels, creams, pastes, or liquids must be less than three ounces in size, and that they should be presented to security staff in clear plastic bags. Tweezers, nail files, glasses repair items, and hairbrushes are all permitted on board aircraft.

If you are disabled or take medications, make sure that all of your medications are in the original containers, which clearly identifies the prescription, who issued it, and the prescription holder, which should match the name on the boarding pass. You may also want to bring medical documentation of your condition. Items such as wheelchairs and canes are not prohibited items, but they will be screened by security staff. Because of the longer security screening for disabled passengers, plan on arriving at the airport early so that you do not miss your flight.

Airlines also have restrictions on the amount of carry-on luggage allowed. Make sure that you know the weight and size limits before you arrive at the airport, so that you do not have to shuffle things into your checked luggage at the last minute. Many airlines have limited carry-on luggage to a single bag. Most of the prohibited items on this list be carried in checked luggage including unloaded weapons, as long as they are packed in secure containers and declared to the airline at check in. Only explosives are forbidden from all areas of aircraft.