Home / Why Are There Liquid Restrictions at Airports? The Story Behind the Rule
Today, when you travel, pulling out your tiny bottles and squeezing them into a clear plastic bag at security feels like just another part of the airport routine. You grab your water bottle, lotion, perfume, and put everything into that one little plastic bag without even thinking twice. But if you had flown twenty years ago, you could’ve walked onto the plane with a full-size drink or a giant shampoo bottle in your backpack, and no one would have stopped you. Things were a lot easier then.
So, what happened? Why did we end up with such strict liquid rules? Let’s break down the full story.
After the terrible terrorist attacks in the United States on September 11, 2001, everything about flying changed. Airports became a lot stricter. Security lines grew longer. There were more bag searches, and new machines checked passengers much more closely. In the United States, the Transportation Security Administration (TSA) was established. Their one job was to make sure that planes and airports stayed safe and that an attack like 9/11 would never happen again.
At the same time, airlines reinforced the doors to their cockpits. They made them stronger and locked them so that no villain could easily break in during a flight. Across the globe, airports have enhanced their security checks. However, one surprising thing stayed the same: you could still carry water bottles, cans of soda, lotion, sprays, and all kinds of liquids through security without any problems.
No one thought much about liquids back then, until something scary happened.
In August 2006, British police stopped a hazardous terrorist plot. Some people had been planning to smuggle liquid explosives onto planes flying from London to the United States. They wanted to disguise the dangerous liquids inside regular drink bottles, such as soda or water, so that the security screeners wouldn’t notice anything unusual. Once on the plane, they planned to mix the chemicals and create bombs right there, mid-air.
The main chemical they planned to use was hydrogen peroxide. This is a chemical that can be very dangerous when mixed incorrectly. It was a risky plan because, at that time, airport X-ray machines couldn’t reliably detect the contents of a liquid bottle. A bomb could resemble a bottle of juice or water.
When the plot was uncovered, governments reacted fast. They couldn’t take any chances.
Right after the plot was discovered, the United Kingdom and the United States immediately banned all liquids in carry-on bags. That meant no water, no coffee, no lotions, no deodorant, and no perfumes. You couldn’t bring any liquids through security, except for baby formula if you were travelling with an infant. Even then, you had to taste it in front of security staff to prove it was safe.
This sudden ban caused massive problems. At big airports like London Heathrow, the baggage systems collapsed under the weight of all the extra checked bags. British Airways alone had to cancel over 1,500 flights within just one week. Airports lost millions of dollars, and travellers were frustrated and confused. Nobody knew exactly what they could or couldn’t bring. Lines at security checkpoints stretched for hours, and many people missed their flights.
The ban was necessary for safety, but it was clear that airports couldn’t maintain it indefinitely.
A few months later, governments realised they needed a more innovative solution. They couldn’t ban all liquids forever because people needed basic things like water, medicine, and personal items. So, they introduced what we now know as the 100ml rule.
Here’s how it works:
This rule allowed people to carry necessary items while still making it more difficult for anyone to smuggle dangerous liquids onto planes.
You might think, “Hey, it’s been almost twenty years! Why can’t they figure out a better system by now?” The truth is, liquid explosives remain one of the most challenging threats to detect. Regular old X-ray machines at airports can’t tell the difference between a bottle of harmless orange juice and a bottle of dangerous chemicals just by looking at them.
Security officers would have to test every single bottle manually, and that would make airport lines even longer. So, until better technology emerged, the 100ml rule was the safest way to allow people to carry liquids without putting everyone at risk.
Finally, after many years, better technology has started to arrive.
Some airports are now using something called CT scanners. CT stands for Computed Tomography. These machines can create 3D images of your bags. They can spin the pictures around and examine everything, including liquids, from different angles. This makes it much easier for security officers to spot anything dangerous without having to open your bag.
CT scanners also utilise specialised computer programs that can automatically detect explosives. This means that one day soon, you may not have to take out your liquids or even your laptop when going through security.
Several airports have already started testing or using these machines, like:
In airports equipped with CT scanners, security lines move more efficiently, and passengers have a much easier time.
For example, London City Airport has installed CT scanners and changed its rules.
Now, travellers there can bring bottles up to two litres inside their carry-on luggage. You no longer need to remove anything at security; simply place your bag on the belt and walk through.
However, even with the new scanners, many airports still limit liquids to containers of 100ml for now, just to be safe.
Although CT scanners represent a significant improvement, they are also costly.
One machine is about the size of a Ford Transit van, and it’s way heavier than old scanners.
Some airport floors couldn’t even hold the weight at first, so they had to rebuild parts of the terminals.
Installing the machines requires a significant amount of time and money. Additionally, security staff require new training to utilise them effectively.
At major airports like Heathrow and Gatwick, with dozens of security lanes, the work is even more challenging.
That’s why many airports missed the original deadline to install CT scanners by June 2024.
Currently, the rules regarding liquids are confusing due to the varying stages at different airports.
Here’s a simple table to show where things stand:
| Airport Status | What Happens |
| London City, Southend, Teesside | No need to remove liquids, up to 2L allowed |
| Heathrow, Gatwick, Manchester, Stansted | Still following the 100ml limit |
| Birmingham, Newcastle, Leeds, Bradford | Liquids stay in bags, but are limited to 100ml |
Even in places with new scanners, most airports still require 100ml per container to prevent mistakes during scanning. That’s why it’s smart to follow the 100ml rule unless you are 100% certain the airport says otherwise.
The United Kingdom isn’t the only place considering changes to the rules.
Other countries are also trying, but progress is slow.
Because every airport and every country moves at its own speed, you should always double-check the rules for wherever you’re flying.
The 100ml liquid rule originated from a genuine threat. People wanted to sneak liquid explosives onto planes, and security needed a fast way to stop them. Even today, almost twenty years later, that rule remains in effect because it works.
New CT scanners are bringing hope. One day soon, we may no longer have to pull out tiny bottles or worry about the size of our hand lotion. But it takes time, money, and training to upgrade airports, and not every place is ready yet. Until then, the best thing you can do is pack smart, familiarise yourself with the rules for your airport, and remember: those small 100ml bottles are still keeping you safe.
The clear plastic bag helps security officers see everything at once without opening each container.
The 100ml liquid rule started in November 2006, a few months after British authorities stopped a terrorist plan involving liquid explosives hidden in drink bottles.
Liquids can be easily disguised as harmless products, such as water or soft drinks. Certain chemicals, when mixed, can form powerful explosives without appearing suspicious.
Yes, you can bring more than 100ml of essential medication or dietary liquid, but you must declare it at security. Officers might ask you to taste it, show a prescription, or provide proof that it is needed.
