What can you bring on a plane: the actual rules, the confusing grey areas, and the things that will get you pulled aside

I once had a jar of tahini confiscated at Helsinki airport security.

A jar of tahini. The security officer was apologetic. The tahini was viscous. The liquid rule, she explained, does not distinguish between tahini and hand lotion, and my tahini was approximately 800ml, which is 790ml more than permitted. I stood there watching it go into the bin and silently mourned it, because it was good tahini from a specific market in Tel Aviv that I’d been carrying home triumphantly.

The rules around what you can bring on a plane are mostly logical once you understand the reasoning, occasionally baffling, and occasionally enforced with a discretion that appears random from the outside. Here is the comprehensive version.

The liquid rule: what it actually says

The “3-1-1 rule” used in the US, UK, EU, Australia, and most other countries:

Individual containers: maximum 100ml / 3.4oz each
All containers: must fit in a single clear, resealable plastic bag no larger than 1 litre / 1 quart
That bag: must be removed from your carry-on at the security checkpoint and placed in the tray separately

This rule applies to things that are “liquid, gel, paste, or aerosol.” Which includes: water, juice, shampoo, conditioner, moisturizer, toothpaste, lip gloss, peanut butter, hummus, tahini (RIP), honey, jam, sunscreen, foundation, mascara (somewhat controversially), contact lens solution, and most things that pour, squeeze, or spray.

It does NOT apply to: solid items (solid deodorant, solid shampoo bars, dry foods, solid chocolate), most medications (with caveats, see below), or baby food/formula in amounts needed for the journey.

The 100ml rule is about the container, not how full it is. A 200ml bottle that is half-empty is still a 200ml bottle. The officer isn’t measuring the contents. They’re looking at what the container says. Partially used bottles don’t get a pass on the size rule.

The bag matters. Some airports are genuinely strict about the bag needing to be transparent and resealable. Most airports have large clear bags available at the security checkpoint if you’ve forgotten yours. Bring your own because the airport ones are thin and unreliable.

What the rules are like in specific regions

The 100ml rule is essentially universal among countries with international air services. However:

Japan adds specific restrictions on certain medications (more on this in a moment) and has stricter enforcement of liquids in some categories. Tokyo’s airports run precise security.

Australia has biosecurity rules that apply on TOP of aviation security. Liquids clear aviation security easily. The same liquids may be confiscated at the Australian border if they contain animal or plant matter. Check biosecurity separately from the aviation liquid rule if you’re importing food items.

US domestic vs. US international departures: TSA applies the same 3-1-1 rule to both. Some other countries have different rules for domestic vs. international departures. In general, apply the most restrictive rule (100ml/1L bag) to be safe.

UK post-Brexit: The UK has announced intentions to update its liquid rules to allow larger containers in some airports using new detection technology. At time of writing, implementation is partial and airport-specific. Check your specific departing airport’s current rules, because they have been in flux.

Middle Eastern airports (Dubai, Doha, Abu Dhabi) enforce the rules but duty-free liquids purchased after security are handled carefully. The issue arises on connections: a duty-free liquid purchased in Dubai for a connecting flight through London can be confiscated at the London security point. Always ask at purchase whether your specific itinerary allows it.

Electronics: what goes where

In carry-on: Laptops, tablets, cameras, phones, portable batteries (power banks), e-readers, smart watches. The general rule: electronics with lithium batteries should be in carry-on, not checked luggage.

Why: Lithium batteries are a fire risk in cargo holds. The cabin crew can manage a small battery fire; cargo hold fires are a different problem. For this reason, airlines and aviation authorities want lithium batteries in the cabin.

Power banks: Must be in carry-on. Not allowed in checked luggage at all on most airlines. There are capacity limits: most airlines allow power banks up to 100Wh (roughly 27,000mAh at 3.7V). Above 100Wh and up to 160Wh usually requires airline approval. Above 160Wh is generally prohibited.

Laptops: Remove from your bag at security in many countries (US, UK, EU, some Asian countries). Place in the tray separately. Most modern airports have CT scanners that can screen laptops in bags, but if you’re asked to remove it, remove it.

Cameras and drones: Camera bodies and lenses in carry-on is strongly recommended (checked luggage claims can be rough on glass). Drones in carry-on is fine, though the battery in the drone must comply with the lithium battery rules. Some countries have import restrictions on drones; research before you travel.

Medications: what to carry, how to carry it

Prescription medications in carry-on, in original labeled containers. This is the standard advice and it’s good advice. If the medication is controlled or unusual, carry the prescription itself (printed copy, not just on your phone) and ideally a doctor’s letter explaining the necessity.

Country-specific medication rules are the exception that will actually affect you:

Japan has the strictest medication import rules of any country I’ve encountered regularly. Certain medications common in other countries are illegal to bring into Japan without prior permission (Kenkin certification). These include some cold medications containing pseudoephedrine, Adderall and stimulant ADHD medications, some codeine-containing products, and some inhalers. The consequences for bringing prohibited substances into Japan are not light. Research your specific medications via the Japanese embassy website or Ministry of Health before traveling.

Singapore and UAE have zero-tolerance policies on certain controlled substances, even in small quantities and even with a legitimate medical prescription from another country. Tramadol, in particular, is controlled in the UAE even if legally prescribed elsewhere. Research before you pack.

Saudi Arabia restricts certain medications and applies strict rules to controlled substances. Israel-stamped medications or items may face scrutiny on entry to several countries.

Most of Europe, Australia, New Zealand, and the Americas: Standard approach. Controlled substances require documentation; everything else, bring what you need with original labeling.

Insulin, EpiPens, and other medical devices that require needles/syringes: allowed in carry-on with a doctor’s letter. Airport medical staff are trained to handle this. Have documentation ready.

Melatonin: Prescription-only in the UK, most of Europe, Japan, and Australia; over the counter in the US, Canada. Bring from home if you rely on it.

Food: the surprisingly complicated category

In carry-on: Most solid food is allowed through security in most countries. Crackers, fruit, nuts, sandwiches, protein bars, dried food, chocolate. The issue is the liquid rule for things like yogurt, soup, hummus, honey, peanut butter, tahini.

The practical rule: if you can’t pour it but you wouldn’t exactly call it solid, it probably falls under the liquid rule. Security officers have discretion and a lot of them will let a small packet of hummus through. A 400g tub will be confiscated.

At customs on arrival: The country you’re entering has its own rules about food importation that are entirely separate from aviation security. Australia and New Zealand are the most aggressive enforcers in the world for biosecurity. Undeclared food on arrival in Australia can result in fines of several thousand dollars. If in doubt, declare it. The worst outcome of declaring is they confiscate it; the worst outcome of not declaring and being found out is a fine.

Japan bans fresh fruits, vegetables, meat, and some dairy from many countries. Thailand bans pork products from several countries. Canada, the US, and the EU all have restrictions on plant and animal matter.

Rule: security at departure is about whether you can bring it on the plane. Customs on arrival is about whether you can bring it into the country. These are different rules and both apply.

The things people always try to bring that usually get confiscated

Full-size toiletries. Every week, thousands of people have normal-sized bottles of shampoo confiscated. The rule is 15 years old. It is not changing. Decant into 100ml containers or buy on arrival.

Sharp objects: Scissors with blades over 6cm, most knives, straight razors, box cutters. Not in carry-on. Fine in checked luggage. Safety razors (the blade type) are a grey area that varies by airport; some allow them, some don’t. Disposable razors are universally fine in carry-on.

Sporting equipment: Ski poles, golf clubs, hockey sticks, baseball bats, all in checked luggage only. Tennis rackets are usually allowed in carry-on (no official rule against them, small enough). Yoga mats: technically allowed, practically awkward.

Self-defense items: Pepper spray, stun guns, tactical knives: not in carry-on anywhere. In checked luggage with specific rules (pepper spray must be declared, valve-protected, etc.).

Things that are allowed but will make security difficult

Wrapped presents: Security can ask you to unwrap anything. Don’t wrap gifts until you’re at the destination.

Snow globes: These contain liquid and have failed the 100ml test at many security checkpoints, regardless of size, because it’s impossible to verify the volume of the liquid inside. Check them or buy them at the destination.

Aerosol sunscreen: Fine, within the 100ml rule. But aerosols are X-rayed slightly differently and occasionally get a second look. Not a real problem, just worth knowing.

Realistic toy weapons: Technically allowed as toys. Practically, they’ll cause significant delays at security and may be confiscated anyway. Not worth it.

The most useful habit

Pack your carry-on once as a trial, then run through it mentally as if you’re standing at the security checkpoint. What will you need to take out of the bag? Laptop in its own pocket. Liquids bag accessible at the top. Belt removed before you get in line. Phone out of your pocket before you reach the X-ray machine. Boarding pass and passport immediately accessible.

The people who hold up the security queue are the people who are surprised by this process for the fourth time this year. You don’t need to be one of them.

And leave the tahini at home. Or buy it when you land.