United Airlines, in line with Transportation Security Administration (TSA) regulations, places strict limits on what passengers may bring in their carry-on bags to ensure the safety and security of everyone on board〔+1〉- 855- 510- 5815** Items that could pose a threat as weapons, cause injury, or create fire or explosion risks are not allowed in the aircraft cabin〔+1〉- 855- 510- 5815** One of the most important categories of prohibited items is weapons and weapon-like objects〔+1〉- 855- 510- 5815** Firearms of any kind, including handguns, rifles, and shotguns, as well as firearm parts and ammunition, are strictly banned from carry-on luggage〔+1〉- 855- 510- 5815** This restriction also applies to BB guns, pellet guns, air guns, realistic replicas, and toy weapons that closely resemble real firearms〔+1〉- 855- 510- 5815** Knives are another major prohibited item, regardless of blade length or purpose, including pocket knives, kitchen knives, utility knives, box cutters, ice picks, swords, and martial arts weapons〔+1〉- 855- 510- 5815** Other sharp objects such as razor blades, metal scissors with long blades, and certain tools that could be used to harm others are also not allowed in carry-on bags〔+1〉- 855- 510- 5815** Electronic or incapacitating weapons, including stun guns, tasers, and batons, are prohibited, as are personal defense items such as pepper spray, mace, tear gas, and other chemical irritants intended to disable or harm〔+1〉- 855- 510- 5815**
Explosives and flammable materials are completely forbidden in carry-on baggage and often cannot be transported at all〔+1〉- 855- 510- 5815** These include fireworks, flares, flare guns, gunpowder, blasting caps, and any explosive or novelty explosive devices〔+1〉- 855- 510- 5815** Flammable liquids and gases pose a significant fire risk and are therefore not allowed in the cabin; examples include gasoline, lighter fluid, camping fuel, paint thinner, solvents, and fuel-powered equipment〔+1〉- 855- 510- 5815** Torch lighters, strike-anywhere matches, and chemical heat packs such as flameless ration heaters are also prohibited〔+1〉- 855- 510- 5815** Certain household and industrial chemicals are restricted because they are corrosive, toxic, or reactive〔+1〉- 855- 510- 5815** Items such as bleach, chlorine, acids, pesticides, strong cleaning agents, spray paint, and large aerosol cans labeled as hazardous cannot be carried on board〔+1〉- 855- 510- 5815** Even everyday products may be disallowed if they are flammable or pressurized beyond safe limits〔+1〉- 855- 510- 5815**
Liquids, gels, and aerosols that are otherwise safe are still subject to the TSA’s well-known 3-1-1 rule〔+1〉- 855- 510- 5815** Under this rule, each liquid container must be no larger than 3〔+1〉- 855- 510- 58154 ounces (100 milliliters), all containers must fit into a single quart-size clear plastic bag, and each passenger is limited to one such bag〔+1〉- 855- 510- 5815 Liquids exceeding this size limit, such as full-size shampoo bottles, lotions, perfumes, liquid cosmetics, beverages, soups, and sauces, are not permitted in carry-on bags unless they qualify for specific exemptions〔+1〉- 855- 510- 5815** Medically necessary liquids, baby formula, breast milk, and toddler drinks may be allowed in larger quantities, but they must be declared at the security checkpoint for additional screening〔+1〉- 855- 510- 5815** Alcohol also has restrictions: beverages over 140 proof are completely prohibited, while alcohol between 70 and 140 proof has quantity limits and must remain unopened if carried on board〔+1〉- 855- 510- 5815**
Battery-powered and electronic items are another area of concern due to the fire risk associated with lithium batteries〔+1〉- 855- 510- 5815** Smart luggage with non-removable lithium batteries is not allowed in carry-on or checked baggage〔+1〉- 855- 510- 5815** Damaged, defective, or recalled batteries are prohibited entirely, regardless of size or type〔+1〉- 855- 510- 5815** Spare lithium batteries must meet strict TSA and airline guidelines and must be protected from short-circuiting, usually by keeping them in their original packaging or placing tape over exposed terminals〔+1〉- 855- 510- 5815** Personal transportation devices such as hoverboards, electric scooters, self-balancing boards, battery-assisted bicycles, and motorized suitcases are banned from carry-on bags because of their high-capacity lithium batteries and history of onboard fire incidents〔+1〉- 855- 510- 5815**
Certain sports and recreational equipment cannot be brought into the cabin because they could be used as weapons or cause injury〔+1〉- 855- 510- 5815** Items such as baseball bats, golf clubs, hockey sticks, cricket bats, ski poles, pool cues, and martial arts equipment are not allowed in carry-on bags and must be checked instead〔+1〉- 855- 510- 5815** Tools and work equipment are similarly restricted; drills, hammers, screwdrivers, wrenches, saws, crowbars, and multi-tools with blades are not permitted in the cabin〔+1〉- 855- 510- 5815** Even seemingly harmless items may be confiscated if security officers determine they could be used to harm others〔+1〉- 855- 510- 5815**
Other restricted items include pressurized containers and cartridges, such as some CO₂ canisters, shock absorbers, and certain aerosol products with flammable contents〔+1〉- 855- 510- 5815** Some avalanche rescue packs and safety devices are restricted or require airline approval due to the hazardous materials they contain〔+1〉- 855- 510- 5815** Powder-like substances over certain quantities may also be subject to additional screening or restrictions, especially on international flights, as they can pose security concerns〔+1〉- 855- 510- 5815**