Carry-on guides
Item pages give you the verdict; these guides teach you the logic, so you can answer the next item yourself. Each one is written from the primary TSA, CATSA, FAA, and CBP sources — the same documents airport screeners work from — then translated into plain English with the exact numbers you need.
Start with the rule you are most likely to get wrong. Most confiscations at US and Canadian checkpoints come from three misunderstandings: what counts as a liquid (peanut butter does), where lithium batteries belong (the cabin, never the hold), and the $10,000 cash declaration (a report, not a limit). Master those three and the individual item pages become quick confirmations instead of homework.
Forced Gate-Checks & Lithium Battery Rules Why lithium power banks cannot fly in the cargo hold, the jetbridge dilemma, and the 2-bag defensive packing strategy. Duty-Free Liquids & Connecting Flights The 48-hour STEB rule, optical Raman bottle scanner traps (Clase Azul ceramic bottles), and US/EU re-screening. Airport 3D CT Scanners & Liquid Rule Rollbacks Why the UK and EU reinstated the 100 ml cap in 2024, C3 scanner software limits, and the round-trip asymmetry trap. Airport Security vs. Border Customs Biosecurity Why clearing TSA does not clear destination customs, $3,300 AUD fines in Australia, and permanent Global Entry revocation. Prescriptions & Controlled Substances Abroad Japan’s absolute Adderall criminal ban, UAE MoHAP online permits, and why foreign customs treats CBD as narcotics. Scissors, Tools & Sharp Objects on Planes The official pivot fulcrum measurement rule, US 4-inch vs EU 6 cm limits, safety razor segregation, and trekking pole bans. Souvenirs, Beach Sand & Cultural Artifacts Sardinia €3,000 sand fines, CITES protected corals, snow globe tennis ball rules, and dense metal X-ray opacity. TSA Screener Discretion & Confiscation Alternatives Understanding 49 CFR § 1540.111, voluntary abandonment vs confiscation, and the 5 legal ways to save your property. The 3-1-1 Liquids Rule, Explained What counts as a liquid, the exceptions nobody tells you about, and how to fit a week of toiletries in one bag. Batteries & Power Banks on Planes Why lithium goes in the cabin, never the hold — and how to read the Wh limit on any label. Flying with Medication Liquid exemptions, cooling packs, controlled drugs, and what to say at the checkpoint. What Food Can You Bring on a Plane? Solid food flies free, spreads are liquids — plus the international customs trap that actually costs you money. How Much Cash Can You Carry on a Flight? No limit domestically; the $10,000 declaration rule internationally — and how to fly with large sums safely. Can You Bring a Vape on a Plane? Cabin only, never checked — plus the on-board use and charging bans most travelers learn the hard way. TSA vs CATSA: The Rules That Change at the Border The liquids rule is identical — bowling balls, powder caps, eye drops, pepper spray and cannabis are not. Every verified divergence in one table. Aerosols on a Plane: TSA 3-1-1 + FAA Checked Caps Spray cans fly under two rulebooks: 3.4 oz in the cabin, 18 oz / 70 oz FAA caps in checked — and cooking spray is banned outright.