New technology could spot a potential bomb
The fear of a bomb being disguised in a soft drinks bottle has led to huge restrictions on passengers carrying liquids on board aircraft.
The chaotic scenes at Britain's airports following 10 August 2006 are hard to forget: seemingly endless queues, security officials asking mothers to taste formula milk - and thousands of exhausted travellers waiting to go on their holidays.
Three men have now been found guilty of conspiracy to murder following the inquiry which led to the restrictions suddenly being brought in - although the jury at Woolwich Crown Court was unable to agree on whether the three had actually planned to target aircraft.
But for the ordinary traveller, the way we pack and travel seems to have changed forever.
A spokesman for the Department for Transport has said the restrictions imposed two years ago will stay in place as the threat level to national security remains "severe".
He also said: "We will continue to work with international colleagues to develop technological detection methods which could ease the restrictions."
Does it remain impossible to relax the rules that passengers say blight their attempt to reach a place in the sun?
Are travellers destined to a lifetime of measuring and decanting essential liquids into 100 ml bottles? Will they be inserting them into plastic bags of the correct size and transparency? Well, not necessarily so.
The restrictions introduced in August 2006 had one purpose in mind: to prevent liquid explosives being brought on board a plane. And the main rules remain the same:
- No liquid in containers larger than 100ml - excluding essential medicines
- "Liquid" includes drinks, syrups, creams, mascara, gels and pastes
- Baby food must be tasted by an adult passenger
- All items should go in a clear 20cm square plastic bag
The reason for these onerous restrictions is simple: most airport X-ray machines cannot differentiate between a bottle of shampoo and a potentially threatening ingredient.
Up to 100ml of liquid is allowed because experts think it is difficult to construct such a small viable bomb.
We are also allowed to buy whatever size of item we wish in the duty-free shops because all items on sale airside have to undergo strict security screening before they can go on the shelves.
But there is good news on the horizon.
Security-screening apparatus is becoming ever more sophisticated - and technology now exists which could enable passengers to take most liquids of any size in hand baggage.
The new X-ray machines can measure the density of liquids and create three-dimensional views of items in luggage.
Delays: Airports thrown into chaos in August 2006
This means that innocuous soft drinks can be eliminated from inquiries - whereas a potentially explosive substance will be instantly outlined in red, prompting its owner to be questioned further.
The arrival of this apparatus would be a blessed relief to the confused, forgetful or just downright hurried passengers who currently jettison prohibited items at the security gate - not to mention avoiding the mountains of waste that have accumulated at airports.
So why are they not already in place at security gates from Glasgow to Gatwick?
Well, in some instances they are. BAA has already 180 of them installed at passenger search areas at the seven airports it owns, including Heathrow. But at the moment they are only operating in the conventional way.
This is because the government is testing the new systems - and the roll-out is still some time away.
Tony Crane is with Smiths Detection, a company that has been pioneering the new technology.
"We have to be absolutely sure that security is not compromised and we will be weighing up the accuracy of the detection during these trials," he said.
"But we are hopeful that the technology could be made available by next year."
This would entail the introduction of almost 600 new machines, if all of the UK's airport were to be included, at the cost of £80,000 per machine - or £48m in total.
But when it comes to airport security, as one problem is resolved, another rears its head.
There were worries that the increased use of common departure lounges for passengers on both domestic and international flights could lead to breaches of security.
New terminals: Fingerprinting a possibility
This led to plans to introduce the fingerprinting of passengers at Heathrow's new Terminal 5, which is designed exclusively to handle British Airways customers.
Officials wanted to avoid the prospect of a potential security risk on an incoming international flight swapping tickets with an accomplice on a domestic flight - in order to avoid immigration checks.
This plan was withdrawn following objections from the privacy watchdog, the Information Commissioner.
Terminal 5 now relies on photographing passengers on domestic flights - a tried and tested method used at Manchester Airport, for example, which also has a mixed departure area.
But a spokesman for the UK Border Agency (UKBA), part of the Home Office, confirmed fingerprinting was still under consideration.
"If airports mix domestic and international passengers, then we will consider requiring fingerprint checks to maintain security," he said.
"But if airports decide to have joint departure lounges it's up to them, not UKBA, to satisfy the Information Commissioner that the right data protection is in place."
And it is here that your journey as an ordinary passenger has become the stuff of international politics.
The so-called "visa waiver program" means many people can fly freely from the EU to the US. European leaders have lobbied Washington to ensure that this important agreement isn't ditched.
But the US Department for Homeland Security is concerned about possible threats - and new rules now mean passengers should submit more information about themselves and their travels in advance.
With or without new X-ray machines, air travel may not be entirely plain sailing for passengers in the future.