August 2011 and you're travelling light. In one pocket is your wallet - no cash, just credit cards - and your intelligent passport, its chip loaded with your encrypted iris scans and fingerprints. Except for the odd bit of lint, the other pockets are empty. Everything else you'll want on your trip - from toothpaste to contact lens solution - was collected the night before by a secure luggage-forwarding service. Only the keys to the house and car remain, and those you can leave safely with the car park attendant at Heathrow's new Terminal 5C.
The future of aviation may not be quite that stark, but it is certain to be more bleak than it was only a couple of weeks ago. Even after the present chaos in the departure lounges is sorted, flying is likely to be less spontaneous and more expensive.
The last thing security experts are predicting is a return to business as usual. "We've crossed a Rubicon," says Simon Stringer, a consultant with Kroll Security. "If anything, you're going to see far more draconian restrictions."
Michael Chertoff, America's Homeland Security Secretary, promptly proved him right by announcing that, by early next year, airlines will have to give his officials the passenger lists for all US-bound flights, and then wait for them to be checked before take off. And John Reid, the Home Secretary, persuaded several of his European counterparts that British-style bans should be introduced across the EU
But with delays and cancellations making air travel a confusing, unprofitable misery, pressure from passengers, airlines and airports for a more sensible regime is growing.
And while they may not change the regulations, their complaints will probably lead to procedures that work more smoothly within the rules.
Such as having your bags picked up a day early so they can be thoroughly scanned, probed, sniffed, sampled and examined prior to departure. Your security-approved, carry-on luggage would be waiting for you on the other side of the passenger checks. So too, would be the shops, stuffed with goods that have similarly been cleared to fly. Already you can buy anything from vin ordinaire to Chanel No 5 at duty free and take them anywhere - except America. And if the blanket ban on cabin luggage returns, airlines may have to look at providing toys for children, potboilers for their parents and laptops for their business passengers.
Aviation security has been an issue for decades; hijackings are almost as old as powered flight itself. Rebel Peruvian soldiers staged the first recorded attempt when they tried to seize a two-seater Ford Tri-Motor at a southern aerodrome in 1931. Its pilot, an American named Byron Rickards, refused to take them up and a polite stand-off lasted for 10 days until news arrived that the revolution had succeeded. Rickards was released on condition that he give a member of the junta a lift back to Lima.
After the Second World War, hijackings were a way to escape oppressive regimes. Cubans fled to Miami and, sometimes, Americans fled to Havana. The crime boomed after the first - and only successful - attack on an El Al plane in 1968. The next year saw a record 82 hijackings, mostly by members of Yasser Arafat's Palestine Liberation Organisation. The most famous hijacking - until September 2001 - was in 1976 when an Air France jet en route to Israel was diverted to Entebbe airport in Uganda by Palestinian terrorists. Israeli commandos raided the airport, rescuing all but three of the 108 passengers. But the bloody storming of aircraft and terminals is a last resort. Catching terrorists before they attack is immeasurably better.
By 2011, Heathrow's new Terminal 5 will be the most visible front line between good and evil. But even on Friday, security at the building site was impressive. The Gurkhas guarding the gate weren't satisfied with my passport and stamped BAA visitors pass, and sent my guide and me off to get a countersignature from another official.
When it's finished in 2008, T5 will handle all BA's Heathrow flights, about 30 million passengers a year. Departing travellers will move from groundside to airside through a single broad passage on the top floor of the 43-metre tall building, beneath the arching wave of T5's 18,000 ton, steel-and-glass roof. Last week, crews were laying Italian floor tiles - pale composites of marble, granite and quartz - where sophisticated scanners will be installed within the next two years. Below us, on the ground floor and down into the basement, a maze of chutes and conveyor belts is already being tested for the task of moving, sorting and X-raying hundreds of thousands of bags a day.
Even now, T5 looks more like a crystal palace than a fortress, though the knuckle joints that hold up the roof do give it an industrial, "Brunelian", air. Travelling through here will never be perfectly safe. At best, its defences, and those at other airports, can be hardened in the hope that the fanatics will turn to easier targets. If they persist, it will likely be with new tactics; travel experts already fear that the next wave of airline attacks will be made with surface-to-air missiles, more than 1,000 of which have slipped beyond the reach of the world's governments. BAE Systems is testing a modified US military device for use on commercial jetliners. Called Jeteye, it can track incoming missiles and disrupt their infrared guidance systems with a powerful laser.
Or they may revert to older tactics. The alleged plot foiled two weeks ago involved triacetone triperoxide (TATP), the same explosive used for the July 2005 attack on the Underground. And the idea of assembling a bomb in flight from innocuous chemicals is more than a decade old. In the 1995 Bojinka plot, a cell led by Ramzi Youssef, a Pakistani raised in Kuwait and educated in Wales, planned to assemble bombs on 11 aircraft flying out of Manila. A fire in Youssef's apartment, where he had been conducting experiments, exposed the plot and a month later he was arrested in Pakistan. He is now serving a life sentence in America for the first World Trade Center attack.
Security companies have been racing since 2001 to develop scanners able to detect threats to civil aviation. Among them are devices that can see through clothes, and CCTV computer programmes that, it is hoped, will one day be able to identify suspected terrorists even beneath disguises.
But the most pressing need is for something that can spot explosives, and domestic liquids that could be easily turned into explosives. Some reports in the past fortnight have suggested that these are years away. In fact, several are already on the market.
The most common devices involve variations on mass spectrometry, a technique best known for its role in identifying mysterious substances on forensic science programmes such as CSI and Silent Witness. The first such device was developed in 1918 by Arthur Dempster, a Canadian physicist in Chicago who went on to work on the Manhattan project. They work by ionising molecules - giving them an electric charge - then sorting them by weight with magnetic and sometimes electric fields, since the paths of lighter ions are easier to bend than those of heavier molecules. The trick has been to find ways to make these analysers small, fast and accurate enough, to work in an airport setting.
One British company, Smiths Detection, has a range of devices, including hand-held wands that can be poked into bags, and "puffers", which look like a metal-detector gate with glass doors. Passengers stepping into the puffer are blasted with pressurised air to dislodge trace molecules which are then sucked up and analysed. Its customers include HM Customs and the New York Police Department.
A New Zealand company, Syft Technologies, uses a different variation on mass spectroscopy for its scanners. One of the problems with trying to detect TATP is that it breaks down into the common chemicals acetone and water. Even dogs are unable to detect it, says Geoff Peck, Syft's chief executive. His company's device, however, can not only spot traces of the explosive as faint as a few parts per billion, but it can report how many it finds, making an expensive false alarm from a single stray molecule much less likely.
A completely different scientific principle - the Raman effect, discovered by Sir Chandrasekhara Venkata Raman, the first Asian scientist to win a Nobel prize - lies behind the First Defender device sold by Ahura, an American company. First Defender works by shining an infra-red laser on to a liquid, even one in a translucent plastic container, and looking for the rare photons that bounce back with changed wavelengths. The pattern of changes is matched against a computer library to reveal what the liquid is, even if it's a mixture of up to five chemicals.
These technologies have two fundamental weaknesses, however. The first is that they are expensive - a single scanner from Ahura will cost the UK government £27,000. And security generates no profits. Many of the companies that provide security to airports are under pressure to cut costs, particularly in poorer countries. "All airports can see that they must have security, but it doesn't have to be done well," says Henrik Kiertzner, an associate director at Arup, a security and risk group that acted as prime infrastructure consultant to Heathrow's Terminal 5.
"There's a degree of box ticking going on. The tendency is to scrimp on training, salary and personnel development. I'd rather have 10 really bright people with no technology than a dummy with £10m of equipment."
The second great drawback is that none of these security checks is foolproof. Perhaps the best medium-term hope, says Kroll's Mr Stringer, is the kind of intelligence and police work that led to the raids a two weeks ago. Not only did they disrupt a big terrorist operation, but they may have deterred others from trying anything similar. "But that still hasn't solved the root problem," he says. "Trying to understand the motivation of people who are willing to die for their cause and find ways to deter them will continue. That's a longer-term, strategic game."
Current hand baggage restrictions
Passengers may take on board one small bag of 45cm x 35cm x 16cm, including wheels, handles and pockets. Liquids and gels are banned. Parents of infants may bring milk or liquid baby food, but must taste it in front of security personel. Liquid medicines under 50ml may be taken if verified by a pharmacist at the airport. Liquids bought after the security barrier may be taken to all destinations except the US.
Aviation security in 2011
Sophisticated software will use credit card details to check a passenger's air-travel history. Suspicious patterns - trips to Afghanistan followed by the purchase of a one-way ticket to New York - would be reported to security staff, possibly even MI5.
On the day of travel, passengers will be scanned by remote-sensing devices before they even reach the doors of the terminal. Facial-recognition programmes will match their CCTV images against those of known or suspected terrorists and criminals. The Police Information Technology Organisation began building a mugshot database in 2002.
As a passenger enters the terminal, a form of natural radiation given off by the body - one which passes through clothes as if they were transparent - will be picked up by passive,
millimetre-wave cameras, revealing hidden objects such as guns, knives or explosives. The technology was tested at Gatwick in 2002.
Computers will also be watching passengers for unusual behaviours - such as moving against the flow of traffic or loitering outside the security gates, waiting for guards to relax.
Metal detectors will be combined with "puffers" or low-frequency vibration plates, which will shake dust from the passenger. The dust is then sucked into a chemical analyser. An X-ray backscatter scanner, first tested at Heathrow Terminal 4 in 2004, can also see through clothes. Passengers who refuse to go through it on grounds of modesty - it reveals everything - are automatically subject to a hand search.
Finally, an array of biometric devices could check to make sure that the ticket-holder is the same person named on his passport and ID card. Computer chips could carry details of finger, retinal or voice prints for comparison.