And the U.S. Transportation Security Administration has issued new regulations aimed at further tightening already stringent security requirements at airports and on civilian airplanes flying within or to the United States.
These include placing armed air marshals on some U.S. flights and sometimes requiring foreign carriers flying to the United States to do the same; profiling passengers at the time of boarding and assigning them a code; fingerprinting travelers to the United States who require visas; and even preventing passengers, while in flight, from congregating near the lavatories.
Many experts, especially in the United States, welcome the moves. Passengers so far appear willing to put up with additional restrictions in exchange for a feeling of extra security.
But civil liberty concerns aside, some Europe-based analysts question whether all the measures are cost-effective and beneficial. Some suggest that politicians are seeking to boost their standing by feeding into public anxiety, or perhaps to increase the profits of an ever-expanding security industry.
Harvey Simon, news editor of "Aviation Week's Homeland Security and Defense" magazine, generally favors the new security measures. Speaking from Washington, he says for example that the color-coding of passengers flying to the United States will be the result of a sophisticated computer program that is likely to be an improvement over the present profiling system, which is flawed.
The current program, known as the Computer Assisted Passenger Screening System (CAPS) is based on parameters that can be circumvented or are unreliable, as Simon explains.
"The current system is based on such items as whether you're buying a one-way ticket. That's supposed to flag you as possibly suspect. Part of the problem is that everybody knows what the parameters are so they become ineffective, if they weren't already ineffective," Simon said.
The new system, known as CAPS 2, will collect passengers' names, dates of birth, addresses, credit card numbers, passport, and visa details, and other available information, and compare them with terror-suspect lists. It will assign each passenger a color designation -- green to indicate a pass, yellow to indicate a need for further screening, and red to bar the passenger from boarding an airplane.
Armed air marshals are perhaps the most contentious of the new security measures. Simon believes that they will boost in-flight security. But he acknowledges that there are concerns regarding some foreign carriers.
"I went to the training center in New Jersey here in the United States, where they train sky marshals," he said. "The training is extremely sophisticated and they're obviously concerned about those types of incidents where the gun would get into the wrong hands and they train specifically for ploys that would create a diversion in which that would be the objective of the terrorists. I think the concern is not so much with these marshals in the U.S. -- who are, as I say, highly trained -- but [with] the U.S. requirement, recently imposed, that other countries whose airlines fly into the U.S. have air marshals on those flights, because it's not clear that those marshals would be trained to the same standards."
British expert Chris Yates, author of "Airport Security: Standards and Technology" and other publications that track developments in air security, is not so confident. He doubts that the risks posed by having an armed air marshal on board a plane, no matter how well that individual is trained, outweigh any possible benefits.
"It's a very dangerous thing to do to introduce a man with weapons into the closed environment of an airliner at 35,000 feet," he says. "If the sky marshal were required to take action, the likelihood of him sitting right next to the person he had to take action against is virtually zero. And if we were talking about a determined terrorist, bent on destruction if he possibly could, then all he is going to do to protect himself against the sky marshal is to take hostages to start with -- and I personally don't want to be the person taken hostage and held effectively as a human shield."
Yates says security issues must be dealt with on the ground, before passengers are allowed on board. But he questions the benefits of computer profiling programs given the problems with the current CAPS system, which has repeatedly prevented innocent passengers from flying. He places the emphasis on new technology, such as sophisticated screening devices to scan luggage -- some of which have already been introduced.
"I'm talking about the introduction of multiple levels of hold baggage screening -- the bags that go into the cargo hold, which improves the ability to detect anything that might well be concealed in those bags. And certainly on the hardware side, we've introduced such technologies as the computer tomography screening devices, similar to those used in the medical sphere, which effectively show multiple levels of the content of the bag on tiny images on the screen," Yates said.
Few people may be aware that in the United States at present, despite the emphasis on what insiders call "total information awareness" and passenger screening, there exists a major loophole in security in the form of unaccompanied cargo. Harvey Simon explains from Washington, "The issue with cargo is that cargo is loaded on board passenger planes right alongside passengers' checked luggage, right in the belly of an airplane. And whereas the luggage goes through an extensive screening, through explosive detection machines that -- while not perfect -- do screen every bag, these boxes go on the plane without any inspection. Many people have pointed out that you could plant a bomb in a box and send it aboard a plane."
In fact, one shipping service employee recently proved almost anything can be shipped in a U.S. plane, as long as it's wrapped as a parcel.
"There was a case recently in which a man who worked at a shipping company put himself in a box to take a trip home to see his parents and he rode in the box all the way to his destination without being detected. So if you can put yourself in a box, you can put a bomb in a box," Simon said.
Authorities at the United States Transportation Security Administration aim to have a system in place by year's end to screen all packages loaded aboard U.S. aircraft. But even once that hole is plugged, other problems remain, such as the possibility that a terrorist armed with a shoulder-fired missile could shoot down a civilian airliner, as nearly happened in November 2002 with an Israeli plane departing from Kenya.
Ultimately, however, European analysts say people in the United States will have to accept that with finite resources, not all risks of terrorism can be eliminated. Yates says a recent request by U.S. authorities that airlines prevent passengers from queuing up for the lavatories goes too far.
"One can understand why they don't like to have crowds, particularly hanging around the forward lavatories near the cockpit . But I think it does go too far. It's one step away from the U.S. authorities, particularly, requiring that we're all chained to our seats for the duration of the flight. Security should begin and end on the ground. I'm all for measures such as locking the cockpit door and ensuring that it stays locked during the course of the flight. But as far as any further security measures on board the aircraft are concerned, I don't subscribe to the view that we have to have the armed sky marshals, that we should prevent people from queuing for the lavatory, that we should prevent people from walking around," Yates said.
Yates says on purely medical grounds, the U.S. authorities could be letting themselves in for more trouble than they bargain for.
"We've had so much debate in recent years over deep-vein thrombosis, which long-haul travelers are particularly susceptible to. And the current medical advice is that during a long flight, people get up and walk about the cabin. If suddenly they're being prevented from doing so, if one or the other of those people who can't get up and walk around suddenly develops deep-vein thrombosis, who are we going to sue?" Yates said.
It's a fine balance between the need to assure tighter security in the wake of the 9/11 terror attacks -- a conviction that few challenge -- and going overboard, trampling civil liberties, and wasting resources in the quest for an unattainable perfect security. Each new measure that is implemented tends to open a new set of dilemmas. As the old adage goes: "The road to hell is paved with good intentions."