The new rules on carrying liquids through UK airport security

For almost two decades, the queue for airport security has seen travellers hastily gulping down their bottled water and cramming liquid toiletries — limited to 100ml apiece — into a single transparent bag. 

But not for much longer. In 2022, the UK government announced that by June 2024, all major airports in the country would be required by law to install high-tech new security scanners. This would allow airline rules on liquids to be scrapped, among other benefits.

With the promise of speedier queues through departure, it was initially good news. But now, four of the biggest airports — Heathrow, Gatwick, Stansted and Manchester — are on course to miss the deadline, prompting fears of confusion this summer. 

What’s the 100ml rule?

It stipulates that passengers with hand luggage can only take liquids and creams in containers of up to 100ml on board an aircraft. These must be placed in a single, transparent, re-sealable plastic bag, which holds no more than a litre and measures about 20cm x 20cm. The bag must be able to close.

Why was it introduced?

The measures were implemented after a foiled plot by Al-Qaeda in August 2006, during which terrorists attempted to disguise liquid explosives as drinks at Heathrow. 

Why is it changing?

The primary driver is an improvement in security technology. More advanced CT scanners mean that security staff are able to take a more detailed look at passengers’ luggage. As well as negating the need to remove liquids and limit them to 100ml, the new machines mean electronics can stay in bags — without closer inspections —and prohibited items such as weapons and liquid explosives can be better detected. According to Smiths Detection, which makes the scanners, this is thanks to explosives detection algorithms and automated object recognition software.

Why is it taking so long?

Introducing the new machines is a huge financial burden for airports and poses a logistical challenge.“It was always going to be a struggle for the big airports,” a senior aviation source told The Times. “One of the biggest issues they face is fitting the new scanners and retraining staff without impacting the flow of passengers.”

Heathrow, which has 146 security lanes across its terminals, faces the biggest challenge in meeting the deadline, and will have the smallest percentage of new lanes installed come June. A spokesman for Gatwick says it will have made “significant progress” by June but “plans to have completed the operation required to install the remaining scanners in Q1 2025”. Security areas will need to be adjusted at several airports because of the size of the new scanners. The floors in some terminals, especially at Heathrow, need to be reinforced because of their added weight.
“The existing scanner is like a washing machine,” says Nick Barton, chief executive of Birmingham Airport. “The new machines are the size of a Ford Transit.”

What impact are the scanners expected to have?

People failing to remove items from their bags or travelling with large bottles of liquids cause delays at airport security, as they result in additional checks. The new machines are expected to cut wait times dramatically, although the fear is that, in the short term, ‘mixed messaging’ will lead to delays — where airports still have both old and new technology, passengers won’t know what to expect. At London City, which has already completed the upgrade, the average time it takes to conduct security checks is now only three minutes and 45 seconds, down from seven minutes in 2022. 

What will happen this summer, and what’s next?

Discussions are ongoing. Heathrow, Gatwick, Stansted and Manchester are expected to be given an extension until 2025, meaning passengers at these airports will be told to follow existing rules — even though some lanes will have been upgraded — to avoid queues. Other airports are understood to be on course, and passengers will benefit this summer. Along with London City, Teesside Airport has already scrapped the 100ml rule. This change will only affect departures from the UK — arrivals into the country will still have to follow the rules of their outbound airport.

This forms part of a raft of new technologies being introduced over the next decade. Facial recognition and AI are playing a big role: in the future, passengers will board planes without showing documents — faces will be automatically matched to passports. Border Force has also started a process to see e-passport gates replaced with ones that do not require them to be inserted.  

Is the change also happening in the US or elsewhere? 

There are other countries that are looking at amending the rules on liquids in light of the new technology, although the UK is among the first to make a blanket change. Spain is on course to follow suit by 2026, thanks to a phased installation of the new scanners. Some other transport hubs, such as Amsterdam’s Schiphol, Frankfurt and Milan Malpensa, have also installed similar ones, and there are a limited number of lanes at Geneva that passengers can choose to use.

In the US, many airports, such as Atlanta's Hartsfield-Jackson and Chicago's O'Hare, have already installed the new scanners and, in these, the Transportation Security Administration (TSA) has slightly relaxed the rules. Travellers here are generally able to leave their food, electronics and liquids in their bags as they pass through — but rules on keeping liquids travel-sized remain, permitting just 3.4 ounces (100ml) or less in a single one-quart transparent bag. A nationwide rule change is still expected to take some time, due to the sheer number of airports across the country. On the whole, travellers can expect to encounter legacy rules at some point on their travels over the coming years.