AIRPORT SECURITY
Airport security: liquids, electronics and batteries
Most checkpoint queues come from three things: oversize liquid bottles, a laptop buried in the bag, and a power bank in checked luggage. Departure and transfer airports can disagree; pack to the stricter stop.
Quick answers
The bottle is almost empty but labelled 200 ml. Will it pass?
Usually no. The limit is the labelled container size, not how much is left. Decant into 100 ml or smaller, or check the large bottle if that liquid is allowed in the hold.
Why can’t a power bank go in checked luggage?
A spare lithium fire in the hold is harder to fight. FAA and airlines keep power banks and spare cells in the cabin, with 100 Wh a common cap that does not need a special airline OK. Read Wh on the pack, not only the mAh on the advert.
Does every airport still require a 100 ml bag?
Not always. Some CT checkpoints relax the bag. If any airport on the ticket still enforces 100 ml, pack to that rule for the whole journey. Check both departure and transfer.
Can medicine exceed 100 ml?
Prescriptions, baby food and essential medical liquids are often allowed in reasonable amounts, but take them out and declare them rather than mixing them into the wash bag. Follow staff and the official page.
01The airport you are standing in is the rule that applies#
Screening follows the airport where you are in line, not the arrival country on the ticket. London to New York means UK hand-luggage rules on the way out and TSA on the way back. Some airports with CT scanners may stop asking for a separate liquids bag, but if any airport on the ticket still enforces 100 ml, a 200 ml bottle will not survive the whole journey.
When in doubt, pack 100 ml containers, one clear bag and power banks in the cabin. Two extra minutes at home is cheaper than losing a wash bag at a connection. This page is a packing order, not that airport’s sign today.
02Liquids: the limit is the bottle, not what is left inside#
TSA’s 3-1-1 rule and the UK hand-luggage page describe the same family of limits: liquids, gels, aerosols, creams and pastes in containers of 100 ml (about 3.4 oz) or less, inside one transparent resealable bag. The limit is the labelled size of the container. A 300 ml bottle with a sip left still fails.
The table splits the three items that stop the belt. Medication, baby food and medical liquids are often allowed in reasonable extra amounts, but take them out and declare them; do not hide them in the wash bag and hope.
| Item | Usual handling | Typical cap or action | Do not |
|---|---|---|---|
| Toiletry liquids | Clear bag, each bottle ≤100 ml | One bag; follow the airport sign | Use a large bottle that is 'almost empty' |
| Laptop / tablet | Carry-on, easy to remove | Many airports screen them separately | Bury them in checked bags or the bottom of the case |
| Power bank / spare lithium | Cabin only | Often 100 Wh; up to 160 Wh with airline approval | Put them in the hold |
| Prescription / baby food | Carry-on and declare | Reasonable amounts; staff decide | Mix them into an undeclared wash bag |
03Keep electronics where you can reach them#
Laptops, tablets and large cameras usually stay in carry-on. Many airports want large electronics in their own tray; burying them stops the belt while you unpack. Chargers and cables are generally fine in either cabin or hold, but do not treat a device with a cell as if it were a cable.
Drones, battery grips and e-cigarettes need a separate check of departure and arrival rules. Legal at the destination is not the same as allowed at the origin checkpoint. Leave the device at home if you cannot confirm both sides.
04Power banks are rated in watt-hours, not the mAh on the advert#
FAA PackSafe and most airlines keep spare lithium batteries and power banks in the cabin. A common cap is 100 Wh; 100–160 Wh often needs airline approval; larger packs usually cannot fly on a passenger aircraft. Wh ≈ (mAh × V) / 1000. A 20,000 mAh pack at 3.7 V is about 74 Wh and is usually fine in the cabin; a 50,000 mAh “travel brick” may already exceed 100 Wh.
Protect the terminals so keys cannot short the pack: original sleeve, a cap, or tape on the contacts. A laptop with a built-in battery is treated as a device and usually stays in the cabin. Loose spare cells in the hold are a dangerous-goods rule, not a mood at the checkpoint.
05Three packing examples#
Example 1: a 200 ml shampoo bottle that is one-third full. The container is 200 ml, so it fails any 100 ml checkpoint. Decant into 100 ml or less, or check the bottle if the airline allows that liquid in the hold. Example 2: a 20,000 mAh power bank at about 74 Wh goes in a cabin pocket, never in the hold. Example 3: London connecting to New York. Pack the UK sector to GOV.UK; the US sector to TSA. Use the stricter of the two so the second checkpoint does not confiscate the bag.
If a low-cost carrier is on the ticket, the cabin case still has to fit a sizer — that is a baggage rule at check-in and the gate, not the liquids rule at security. Clear security first, then the sizer. This site’s carry-on guide covers size; this page covers what the X-ray will query.
06Empty pockets; documents and medicine on top#
Passport, boarding pass, liquids bag, laptop and any medicine you need in the air should come out in about ten seconds. Before the body scanner, put coins, keys and the phone in a tray or the bag so you are not pulled aside. Belts and heavy coats come off when the sign says so — not after the belt is already moving.
Implants or in-flight injections need whatever card or prescription copy the departure airport asks for. Officers are looking at what is in the bag, not at a screenshot of your itinerary.
07Common mistakes#
A large bottle with 'only a little left'; a power bank in the hold; a laptop at the bottom; assuming every country dropped the 100 ml bag; treating the connecting airport as someone else’s problem. A CT checkpoint that relaxes liquids does not promise the next airport will do the same.
Another is rebuilding the bag in the queue, or pouring out water while keeping the oversize bottle. Buy water after screening. The rule is whatever the airport and airline publish that day; a blog photo is not a pass.
08Checklist before departure#
Read liquids rules at departure and transfer airports; decant toiletries into 100 ml or less in one clear bag; put laptops and tablets on top; carry power banks with protected terminals; keep documents and medicine in their own layer. If you have spare lithium cells, read the Wh on the pack and ask the airline above 100.
This page restates common TSA, GOV.UK and FAA PackSafe points. It does not replace that airport’s sign or the airline dangerous-goods page. Size and weight belong in the luggage calculator; security only asks what you packed and which layer it sits in.
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MORE GUIDES
Keep reading before you go
What to pack for international travel: a checklist that fits a carry-on
Read the airline’s size and weight first, then pack for the number of days. A bag that fits the sizer empty may not when it is full.
Things to do before an international trip: a pre-departure checklist
Most problems abroad start as unfinished chores at home. Work through seven days out, two days out and the departure day, then leave.
How big can a carry-on be before it is turned away?
Limits vary by airline, cabin and fare. First check whether the included piece is an under-seat bag or an overhead cabin case, then measure the packed bag with wheels and handles.