Flying involves navigating rules about what you can and cannot bring, from everyday toiletries to devices and duty‑free acquisitions. This guide explains what is not allowed on flights, how rules differ between checked and carry‑on baggage, and how screening, regulations, and airline policies interact. You will find concrete examples, fast guidance on common edge cases, and sources you can check before you travel. Use this information to pack safely, pass security efficiently, and avoid surprises at the gate or the checkpoint.
Why These Rules Exist and How They Are Set
Aviation security regulations aim to protect passengers, crew, aircraft, and operations from hazards, whether accidental or deliberate. In many countries, civil aviation authorities write baseline rules that airlines and airports then enforce and sometimes tighten. Security screening processes, airspace risk assessments, and incident data shape these measures. Ground staff, flight crews, and security teams apply consistent standards so that safety expectations remain predictable worldwide. Understanding the logic behind the rules makes it easier to comply and to plan ahead.
Prohibited Items: Generally Not Allowed in Any Bag
Some items are broadly prohibited in both carry‑on and checked bags because they pose a high risk to safety, health, or security. These categories are commonly aligned across major regulators, although specific listings and enforcement can vary by country and airline.
- Explosives, fireworks, and devices that simulate them
- Flammable liquids, gases, and solids (for example, fuel, propane, matches
- Highly reactive substances and certain radioactive materials
- Weapons, firearm parts, and realistic replicas that can be mistaken for real weapons
- Projectiles and items designed as weapons or capable of causing serious injury
- Items that authorities declare hazardous on security or terrorism grounds
Security Screening and Prohibited Enforcement
At security checkpoints, officers use X‑ray images, swab tests, and physical inspections to identify prohibited items. If something is flagged, items may be confiscated, you may be referred to law enforcement, and in serious cases authorities can impose fines or legal charges. Screening outcomes depend on what is permitted at the point of departure, transit countries, and the destination. Knowing the baseline prohibited list helps you avoid difficult last‑minute decisions at the checkpoint.
Restricted Items: Allowed Only Under Conditions
Restricted items can travel by air but only under controlled conditions, such as limits on quantity, packaging, or placement in checked baggage. These rules balance practical needs—medicine, tools, or duty‑free purchases—against risk management. Always check airline and destination rules before packing; conditions for children, medical needs, and exceptions can differ.
Liquids, Aerosols, and Gels in Carry‑On Bags
Most regulators follow a common format for liquids in carry‑on baggage: containers must hold 100 milliliters (3.4 ounces) or less, all containers must fit in a single transparent, resealable bag (usually 1 liter capacity), and one bag per passenger is allowed. Exceptions exist for medicines, infant formula, and gels needed for medical or mobility conditions, which can be declared at security. Duty‑free liquids purchased in airside areas are usually exempt from the size limit if they remain in a sealed, tamper‑evident bag with a receipt. When in doubt, keep liquids out of the carry‑on and pack them in checked baggage if permitted.
| Item or Category | Verified Detail | Source Type |
|---|---|---|
| Liquids in carry‑on (general) | 100 mL (3.4 fl oz) or less per container; all containers must fit in one clear resealable 1 L bag | ICAO/IATA baseline guidance |
| Medical/childcare exceptions | Larger amounts allowed when declared and screened; documentation may be required | Regulator guidance documents |
| Duty‑free liquids | Permitted in reasonable quantities in sealed tamper‑evident packaging with receipt; exempt from 100 mL rule | IATA and airport authority policies |
| Checked baggage liquids | Packaged according to IATA packing instructions; some hazardous items remain prohibited | IATA Dangerous Goods Regulations |
Medicines, Medical Devices, and Mobility Items
Prescription and over‑the‑counter medicines, including liquids, are generally allowed in both checked and carry‑on baggage when you declare them at security. Keep medicines in their original containers, bring a copy of prescriptions for controlled substances, and be ready for additional screening. Mobility devices such as insulin pumps, implantable medication pumps, and CPAP machines are usually permitted; you may be asked to demonstrate functionality and, occasionally, to leave components in place during screening. Contact your airline and, when needed, the destination country’s civil aviation or health authority for documentation requirements.
Batteries, Power Banks, and Electronic Devices
Lithium‑ion and lithium‑metal batteries are common on flights but face specific packaging and transport rules. Spare (uninstalled) lithium‑ion batteries and power banks in carry‑on baggage are generally allowed, with limits on watt‑hour ratings (often under 100 Wh without approval, up to 160 Wh with airline permission). Damaged or recalled batteries are prohibited. Installed batteries in devices and electric wheelchairs are usually acceptable, but mobility devices may require screening. Check airline policy and consider travel‑specific battery limits for long‑haul flights.
Checked Versus Carry‑On: Where Things Can Go
Whether an item is allowed often depends on whether it travels in checked or carry‑on baggage. Some items must ride in checked bags with proper packing, while others must stay with you in the cabin. A few items are banned from checked baggage altogether. Knowing this distinction helps you pack safely and avoid last‑minute repacking.
Practical Examples: Checked vs Carry‑On
- Lithium‑metal battery spare cells: usually prohibited in checked bags, allowed in carry‑on
- Small toiletries (100 mL or less): must be in carry‑on if you want them accessible; larger containers can go in checked
- Fragile items and important documents: keep in carry‑on to reduce loss or damage risk
- Pressurized items and certain tools: often restricted or requiring airline approval for checked transport
Duty‑Free and Border Purchases: What You Can and Cannot Bring
Items purchased in airside duty‑free zones can usually be brought on board, provided they remain in tamper‑evident security bags with valid receipts and are within reasonable quantities. However, some destinations restrict agricultural products, plants, animal products, and medications. When flying internationally, verify both departure and arrival rules, especially for food, plants, and medicines. If you are unsure, declare the item and allow officials to inspect it upon arrival.
Smart Packing Alternatives and What to Do If Something Is Prohibited
When an item is not allowed on flights, you often have practical alternatives: ship it ahead, use a different mode of transport, or adjust what you bring. Airline lounges and airport stores may sell common travel items if you forget something. If you must travel with a restricted medical item, contact your airline and relevant authorities in advance, and carry supporting documentation. Planning and clear labeling reduce risk and speed up screening.
Summary of Core Rules
Focus on categories that are broadly prohibited (explosives, weapons, flammables), respect size and packaging rules for permitted items (especially liquids in carry‑on), and verify exceptions for medicines, batteries, and mobility devices. Carrying a copy of key rules, keeping receipts for duty‑free purchases, and confirming airline policies close to departure help you travel smoothly. Safe packing leads to smoother checkpoints and fewer surprises.
Checklist Before You Travel
- Review the airline and destination country rules for medicines, batteries, and special items
- Place liquids and aerosols in a clear, resealable 1 L bag in carry‑on if they are 100 mL or less
- Pack prohibited or restricted items in checked baggage only when explicitly allowed
- Keep receipts for duty‑free purchases and leave items sealed in tamper‑evident bags
- Declare medicines, medical devices, and large battery packs at security
By following these principles, you can navigate what is not allowed on flights with confidence and minimize disruptions at security and boarding.