Carry-On or Checked Bag? What You Can and Cannot Pack, Including Power Banks and Liquids

Aviation security rules are set by national authorities and airlines, and they differ from place to place and sometimes change. Use this guide as a starting point, then check your airline's baggage page and the security page of your departure airport, and of any airport where you will change planes.

Power banks and spare batteries: carry-on only

This is the most important rule to know. Under widely used international dangerous-goods rules, spare lithium batteries, including power banks, must be carried in your cabin baggage. They must not be placed in checked bags.

The reason is fire safety. If a lithium battery overheats in the cabin, the crew can see it and respond. In the hold, a fire would be much harder to deal with.

Some points to remember:

• Size limits. Batteries up to 100 watt-hours are generally allowed in the cabin without special approval. Larger ones, usually between 100 and 160 watt-hours, normally need airline approval and may be limited in number. Batteries above 160 watt-hours are generally not permitted.
• Check the label. Power banks often show their capacity in watt-hours, or in milliamp-hours with a voltage. If only milliamp-hours is shown, the airline can help you work it out.
• Protect the terminals. Keep batteries from touching metal objects. Use the original case, a separate pouch or tape over the terminals.
• Follow your airline's use rules. Some airlines ask passengers not to use or charge power banks during the flight, or not to keep them in overhead lockers. Check your airline's current policy.

Liquids, gels and aerosols

Many airports limit the liquids you can take through security. The common version of the rule is that each container must be no more than 100 millilitres, and all containers must fit in one transparent, resealable bag. In the United States the same rule is described as 3.4 ounces per container.

Some airports with newer scanning equipment allow larger containers, so the rules are not identical everywhere. If you are transferring between airports, apply the stricter rule.

Exceptions usually exist for essential medicines and baby food or milk. You may need to tell the officer and show them separately. Check the guidance for your airport.

Anything over the limit should go into checked baggage if you are checking one.

What cannot go in carry-on

Rules typically ban sharp or dangerous items from the cabin. Examples are knives, scissors with long blades, tools, and sports equipment such as bats. Some small items may be allowed in some countries. If you are unsure, put it in your checked bag, or leave it at home.

What cannot go in checked bags

Some dangerous goods are restricted in checked baggage as well. Besides spare lithium batteries, these include things like flammable liquids, compressed gases and certain chemicals. Lighters and matches have specific rules that vary by country. Your airline's dangerous goods page lists the details.

Medicines and important documents

• Keep medicines in your carry-on so you still have them if your checked bag is delayed or lost.
• Carry a prescription or doctor's note for controlled or injectable medicines when travelling internationally.
• Keep passports, money, keys and valuables with you, not in checked baggage.

Electronics and cables

Laptops, tablets and cameras usually travel in the cabin. At some airports you may be asked to take larger electronics out of your bag at security. Keep them easy to reach.

Size and weight limits

Airlines set their own limits on the size and weight of cabin and checked bags. Budget airlines can be strict about cabin bag size and may charge at the gate. Measure and weigh your bag before you leave home.

A simple packing routine

1. Put batteries, power banks, medicines, valuables and documents in the cabin bag.
2. Put liquids in containers of 100 millilitres or less in one clear bag, and keep it at the top.
3. Check pockets and bags for sharp objects before you reach the airport.
4. If in doubt, ask the airline before you travel, not at the airport.

The takeaway

If you remember only one thing, let it be this: power banks and spare batteries go in your cabin bag, never in checked luggage. For everything else, the safest approach is to check your airline's and airport's pages before you pack.