100ml liquid rule at UK airport: What is changing?

Many airline passengers say the worst part of any journey is the airport security check. Worldwide, an average of half a million people pass through airport security every hour. Travellers resent the limit on LAGs (liquids, aerosols and gels) in cabin baggage, as well as the obligation to extract electronics such as laptops and tablets from hand luggage.

The liquids rules were introduced hastily worldwide in 2006 as “a temporary measure” to protect against explosives. Despite repeated promises they remain in place.

In 2019 Boris Johnson vowed the rules would be eased at major UK airports by 2022, allowing larger quantities and eliminating the need to have liquids separately scanned. Rishi Sunak’s government then extended that deadline to 1 June 2024.

While new scanners are being installed at checkpoints at all the UK’s main airports – the work was not fast enough to meet the June deadline.

The big four UK hubs – Heathrow, Gatwick, Manchester and Stansted – said several months ahead they would not be ready in time. The then-transport secretary, Mark Harper, granted airports an extension, but warned that they could be fined if they further delay the roll-out of smoother security.

A week after the deadline, progress in aviation security actually went into reverse, with the Department for Transport (DfT) ordering airports with the new equipment to restore the old 100ml limit on LAGs.

Simon Calder, former security officer at Gatwick airport and current Independent travel correspondent, explains more.

Cabin baggage: what are the rules?

The list of items that cannot be taken through an airport security checkpoints in carry-on bags has increased over the decades. Prohibitions have evolved in reaction to terrorist attacks – successful and otherwise.

All weapons, whether firearms, knives or explosives, are banned from hand luggage. But there are also strict rules about larger quantities of liquids, aerosols, gels, pastes, lotions and cosmetics, extending even to yoghurt, soft cheese and Creme Eggs.

For passengers, the best plan is to assume that no container for any liquid, aerosol or gel can be above 100ml.

At most airports LAGS must be carried within a resealable clear plastic bag with a maximum volume of one litre, and removed for the security check. But at seven UK airports with advanced equipment already installed, the liquids can be left in the passenger’s luggage.

How did the liquids rule come about?

In August 2006 the aviation industry – and baffled passengers – awoke to find security rules for passengers had tightened overnight. The government announced that it had uncovered a terror plot to blow up transatlantic jets from Heathrow to North America.

The perpetrators aimed to take the ingredients for improvised explosive devices on board a number of aircraft. The ingredients, derived from hydrogen peroxide, were intended to be smuggled aboard in soft drink containers. The plotters aimed to assemble the bombs on board before detonating them and destroying the plane. They were later convicted of offences including conspiracy to murder and conspiracy to cause explosions.

The bosses of Britain’s airlines were called in the early hours of 10 August 2006 to be told their passengers would be banned from carrying anything more than a purse or wallet into an aircraft cabin. Even pens were banned from transatlantic flights, on the grounds that the ink they contained was a liquid.

One concession was made, for nursing mothers: they could take milk for their baby through the checkpoint, but only if they tasted it first in front of security staff to demonstrate it was the real thing.

Baggage systems could not cope with two or three times the normal number of items, and Heathrow airport ground almost to a standstill. Flight networks elsewhere in the UK and Europe were also affected.

Three months later, the rules were eased – but with strict limits that prevail today at almost all UK and overseas airports.

Were they always intended to be permanent?

No. The limits were introduced as a “temporary measure” while airport security technology caught up. But progress has been painfully slow.

Even a very modest relaxation of the rules – to allow airport purchases of drinks to be taken through checkpoints in a sealed “security tamper-evident bag” (Steb) – took years to be implemented. Many passengers are still being caught out, losing their expensive airport purchases, because duty-free drinks are not allowed through the airport where they change planes.

Is there a technological solution?

Yes. Modern scanners use computed tomography (CT) – the same technology as medical scanners – to analyse the molecular structure of the contents of a passenger’s bag. The machines can detect potential threats and present security officers with a three-dimensional image of the contents.

They can also analyse whether laptops and other electronic equipment present a danger.

At airports where the technology is installed, liquids and laptops no longer have to be removed.

The aim is that security should be enhanced, with more sophisticated assessment of potential threats. The amount of staff time consumed in “secondary searches” should be reduced, allowing officers to spend more time assessing passenger behaviour.

Travellers have a much easier experience: they no longer need deconstruct their cabin bags, and the whole airport process feels much smoother and less stressful.

That sounds great – so what are we waiting for?

The new kit was first used in Europe at Shannon in the west of Ireland, where “liquids, gels, pastes, lotions and cosmetics in containers of any size” have been allowed through security since March 2022.

To reduce stress for passengers and increase security, in 2019 the government told all major UK airports to have advanced CT scanners at security checkpoints by 1 December 2022. But the deadline was missed.

During the Covid pandemic, airports faced catastrophic losses as passenger numbers collapsed. The obligation to make the multi-million pound investment required was lifted.

In 2022, the then-transport secretary Mark Harper promised the airport experience would become easier from 1 June 2024: “The tiny toiletry has become a staple of airport security checkpoints, but that’s all set to change. I’m streamlining cabin bag rules at airports while enhancing security.

“By 2024, major airports across the UK will have the latest security tech installed, reducing queuing times, improving the passenger experience, and most importantly detecting potential threats.”

How did that turn out?

Badly, with the vast majority of airports failing to meet the deadline. They include the UK’s four biggest airports, which handle most of the nation’s passengers: Heathrow, Gatwick, Manchester and Stansted.

A senior aviation figure, Jonathan Hinkles, told Airliner World: “For airports – many still battling to repair their financial balance sheets after the pandemic – the huge cost of this new equipment is an unwelcome burden.

“The government-imposed deadline date deprived them of any real ability to negotiate prices with suppliers of the new equipment, and much of the new kit is turning up late too.”

In April 2024, the government said: “We recognise that installing the new security equipment at busy airports has been a logistical challenge, with some airports having to undertake significant construction work to allow the new, extremely heavy equipment to be fitted. In some cases, airports have been required to construct entirely new screening halls.”

Mr Harper said: “It’s important we give those airports yet to meet the deadline a second chance to get the job done.”

The then-transport secretary said aviation security law would be changed so non-compliant airports could be fined – though that legislation was scuppered by the election being called.

Some complied, though?

Yes. Seven airports met the 1 June 2024 deadline: Aberdeen, Newcastle, Teesside, Leeds Bradford, Birmingham, Southend and London City. In addition, Bristol airport says it will have the new equipment fully in place by 14 June 2024.

They saw having the kit in place as a competitive advantage, with the promise of an almost complete relaxation of the liquids rule – with up to 2 litres being allowed through.

But in a shock move, from 9 June 2024 they were ordered to restore the 100ml limit. It was not a complete reversal; passengers will still be able to leave liquids, aerosols, gels, etc, in their cabin baggage. They must, though, be in containers of 100ml or less.

Why did that happen?

It was not the airports’ choice. At London City and Teesside, for example, the new scanners have been working well for over a year.

A Department for Transport spokesperson said: “This temporary move is to enable further improvements to be made to the new checkpoint systems.”

Mr Harper later said: “We’ve reintroduced that rule while updates, changes are made to the scanning equipment at the airport to make sure we can continue delivering our world-leading levels of aviation security.”

The Independent understands the move has nothing to do with fears of weaker aviation security. Instead, it resulted from concerns about long queues at UK airports as the summer rush – amplified by football fans departing for Euro 2024 in Germany.

Ministers fear that delays at security checkpoints could build up because the new equipment is mis-identifying many innocuous items in passengers’ baggage as posing a threat.

Sources have told The Independent that harmless liquids such as sunscreen have been misidentified as high-threat substances. The potential converse is that dangerous liquids could be passed as safe.

While security has never been compromised, a number of airports using the new scanners have experienced long queues due to a higher-than-expected rejection rate, with security officers obliged to carry out hand searches of cabin baggage.

On several occasions while passing through checkpoints at non-fully compliant airports with the new kit, I have witnessed the system snarling up due to the large number of bags required to undergo a hand search – and gone from imagining I had plenty of time for a coffee before the flight to sprinting to the gate.

If sunscreen shows up as a possible threat, why does the quantity matter?

Because the 100ml limit was selected as a sufficiently low volume to avoid an on-board threat. Effectively, the airports with new scanners can pass bags that would otherwise be rejected. The aim is to speed up the process and reduce queues.

When everyone is ready, will that be the end of problems?

Not necessarily: passenger confusion is a constant problem for aviation security. It was difficult enough conveying the two sets of rules, “old” and “new”, for items carried in cabin baggage. Because of the publicity surrounding light-touch security at a handful of airports, there are fears that travellers may infer rules have changed everywhere.

Worldwide, lack of conformity is a key issue for aviation security professionals – and passengers.

At many airports liquids are limited but can stay in the traveller’s bag. Laptops and tablets such as iPads must be removed in the UK and many other countries, but in some nations they need not be.

The European Union (and wider Schengen Area) has also reverted to the “old” rules at all airports from 1 September 2024, following concerns about the new equipment installed at some airports. Olivier Jankovec, director general of the airports’ body ACI Europe, said: “Those airports which have been early adopters of this new technology are being heavily penalised both operationally and financially.”

In Israel, procedures are entirely different. The authorities say: “Passengers should arrive three hours prior to departure for the security check procedure.” There is sometimes intense questioning by officials, and laptops must be removed. But liquids are permitted without restriction.

The main issue: passengers should not expect aviation security to be the same worldwide – or even UK-wide. At some small Scottish airports including Barra, Campbeltown and Tiree there have been no security checks since 2017.

Is this going to cost me more?

The airports that are collectively investing hundreds of millions of pounds will be seeking a return – and that could include raising fees. But the long-term aim is that new tech should cut staff costs, representing savings for airports.

Willie Walsh, director-general of the International Air Transport Association (Iata) – representing airlines worldwide – said: “Implementing this technology should not come with a big bill. In fact, simplified processes should deliver significant efficiencies.”

“Speedy deployment should be possible. The technology has already been used successfully and for a long time at various airports across the world with measurable improvements to the passenger experience.”

Will aviation security remain a permanent pain?

No. In 2019 Iata described the prevailing security situation as “no longer sustainable”. It has been working with airports for over a decade on a project called “Smart Security”.

Ultimately walk-through metal detectors and security pat-down of many passengers should be eliminated, with technology assessing possible threats more effectively than humans watching screens.

The passenger should be able to walk unchallenged along a corridor flanked by detectors, barely aware that they are being checked.

Checkpoints will still be staffed, but security personnel will be freed up to do what people do best, which is to study the behaviour of passengers and identify “persons of interest” for further investigation.

However, as the reversals at UK and EU airports show, there is a long way to go.