Passenger planes remain the prime target of terrorists intent on committing mass murder and gaining worldwide notoriety.
Global rules took effect with the United Nations’ Convention for the Suppression of Unlawful Seizure of Aircraft in 1971.
Since then, aviation security has become progressively more invasive, undignified, time-consuming and expensive; the Department for Transport insists security measures must be applied “consistently and competently”.
Airport security is a pain point for passengers, who have to comply with a tricky range of rules on what they can bring on board an aircraft.
But a trial of new scanners at Europe’s busiest airport, Heathrow, could herald the end of hand-luggage liquid restrictions in the UK – and potential be extended worldwide.
I formerly worked in airport security at Gatwick. Allow me to explain the issues.
Q Why was the “liquids ban” introduced, and how long has it been in effect?
Restrictions on liquids, aerosols and gels (LAGs) in passengers’ cabin baggage were imposed from dawn on 10 August 2006.
In the early hours of that morning, the government announced it had uncovered a “liquid bomb plot”. It was described as the largest terror plot ever discovered in Britain.
Terrorists planned to board transatlantic flights with the ingredients for improvised explosive devices, disguised in soft-drink bottles, in their hand luggage. They intended to assemble the bombs on board and detonate them in a bid to destroy the planes and kill everyone on board.
In response a near-total ban on liquids was introduced at UK airports. Even pens were being banned from cabin baggage because of the ink they contained.
The strict new rules immediately brought Heathrow and other airports almost to a standstill. In the following week, British Airways alone cancelled over 1,500 flights.
Three months later, the near-total ban was eased in the UK, and common rules on LAGs were imposed worldwide.
Q Just remind me of the rules?
Anything which can be regarded as a liquid is not allowed to be taken through airport security in a container of more than 100ml. That includes obvious candidates - drinks, shampoo, sun lotion - but also toiletries such as aerosol deodorants, hairspray, hair gel, mascara and cosmetic creams. Food, too: jam, honey and (in many cases) cheese are also banned in containers over 100ml. “Note that liquid/solid mixtures of food, such as solid food in a sauce, are also considered liquids,” says the CAA.
Bear in mind it is the volume of the container that is significant. Even if you have a 125ml tube of toothpaste that is very evidently almost finished, it will be confiscated.
That might sound harsh, but the idea is that security staff do not have time to assess the amount of liquid in containers that are not full.
Liquids in containers of 100ml or less must be placed in a resealable, transparent plastic bag measuring around 20cm by 20cm. Each passenger can carry only one.
Exceptions are made for medicines in containers over 100ml, which require “medical confirmation” – such as your name on a prescription label or a letter from your doctor. “These conditions only apply to prescription medication,” says the CAA. “Over-the-counter medicines are subject to the same restrictions as toiletry/cosmetic liquids.”
When travelling with a baby, milk and baby food can be carried in containers larger than 100ml.
Q Besides annoyed passengers, who is calling for change?
The airlines, airports and European Commission are frustrated that restrictions imposed almost 12 years ago were only ever intended to be short-term measures.
The International Air Transport Association (IATA) says of current aviation security practices: “Today’s model is not sustainable in the long term.”
Five years ago the European Commission pointed out: “This ban was envisaged as a temporary restriction to be lifted when suitable technology to screen liquids for explosives became readily available.”
Q What is the new technology being deployed at Heathrow?
Computed tomography (CT) scanners, which originally began as medical technology. By analysing a series of two-dimensional scans from different angles, they produce 360-degree images which allow staff to examine objects more closely, and can highlight potentially explosive materials from the way the X-rays interact with the molecular structure.
During the trials at Heathrow, normal security checks will be carried out in parallel. But if these trials prove successful, the security search should be able to rely on CT to reveal any liquid in hand luggage that poses a threat. Were this to happen, the liquids ban could be revoked.
Q So when will things go back to the way they were before 2006?
Assuming the tests are successful, ideally the technology would be rolled out across the world. IATA says: “CT screening equipment is becoming mature enough for large-scale implementation”.
But given constraints on how quickly scanners can be made, and the costs involved, I predict there is no prospect of CT being standard at major airports worldwide in less than a decade. It is likely that either the US or the European Union will be first to relax the liquids rule.
America’s Transportation Security Administration (TSA) says it is keen to explore CT-based solutions for screening, not least to reduce costs.
Q Any downside?
Once airports in one region start easing cabin-baggage rules, it will trigger confusion and frustration for passengers starting or ending journeys elsewhere in the world. Liquids that are allowed in the cabin of flights departing from the EU may not be permitted on onward connections in Dubai, Istanbul or Toronto.
Even Europe’s recent modest relaxation of the rules - to allow airport purchases of drinks to be taken through checkpoints in a sealed “security tamper-evident bag” (“STEB”) – is causing confusion. Many passengers are still being caught out, and losing their expensive airport purchases, because they were bought at an airport outside the permitted zone.
Q Could technology ever remove the need for physical checks at airports?
Yes, that is the goal of the airlines and airports. They are well aware how much passengers dislike the queues for security, and how much the security operation costs.
For years they have been working on the concept of “Smart Security”. IATA calls it: “A continuous journey from curb to airside, where passengers proceed through security with minimal inconvenience.”
The aim of Smart Security is that, ultimately, the “walk through metal detectors” and security pat-down of many passengers should be eliminated. Technology will assess material threats more effectively than humans watching screens. The passenger should be able to walk unchallenged along a corridor flanked by detectors, barely aware that he or she is being checked.
Checkpoints will still be staffed, but security personnel will be freed up to do what people do best: to study the behaviour of passengers and identify “persons of interest” for further investigation.
But for years to come, it is safe, if disheartening, to assume that airport security rules will remain more or less as they are.
Q Meanwhile, is there no prospect of relaxation?
Some aviation security professionals say that injecting unpredictability into airport security, with many passenger experiencing lighter-touch checks, will result in better detection and lower costs.
At Campbeltown in Scotland all security restrictions were lifted in January 2017. For the first time in nearly half a century, a scheduled flight took off from an airport on the British mainland without the usual security checks for passengers or their possessions.
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies