The debate over profiling airline passengers revived after the thwarted Islamist plot to bomb 10 airplanes in London on August 10. The sad fact is, due to a mixture of inertia, denial, cowardice, and political correctness, Western airport security services - with the notable exception of Israel's - continue to search primarily for the implements of terrorism, while largely ignoring passengers. Although there has been some progress since 9/11, most involves the scrutiny of all travelers' actions. For example, in 2003, the US Transportation Security Administration, charged with protecting American airplanes, launched a passenger profiling system known as Screening of Passengers by Observation Techniques, or SPOT, now operating in 12 US airports. Adopting techniques used by the US Customs Service and by Israeli airport security, SPOT is, according to TSA spokeswoman Ann Davis, "the antidote to racial profiling." Relying on "behavioral pattern recognition," it discerns, she says, "extremely high levels of stress, fear and deception." SPOT agents observe passengers moving about the airport, with TSA agents looking for such physical symptoms as sweating, rigid posture, and clenched fists. A screener then engages "selectees" in conversation and asks unexpected questions, looking at body language for signs of unnatural responses. Most selectees are immediately released but about one-fifth are interviewed by the police. After the London plot, the British authorities have instituted a crash-course in SPOT, learning directly from their American counterparts. Building on this approach, an Israeli machine, called Cogito, uses algorithms, artificial-intelligence software, and polygraph principles to discern passengers with "hostile intent." In trial runs with control groups, the machine incorrectly fingered 8 percent of innocent travelers as potential threats and let 15 percent of the role-acting terrorists slip through. WHILE METHODS that target the whole population have general value - SPOT did discover passengers with forged visas, fake IDs, stolen airline tickets, and various forms of contraband - its utility for counterterrorism is dubious. Terrorists trained to answer questions convincingly, to avoid sweating, and control stress should easily be able to evade the system. The airport disruptions following the thwarted London plot prompted much discussion about the need to focus in on the source of Islamist terrorism and to profile Muslims. In the words of a Wall Street Journal editorial, "a return to any kind of normalcy in travel is going to require that airport security do a better job of separating high-risk passengers from unlikely threats." This argument is gaining momentum. A recent poll finds that 55 per cent of Britons support passenger profiling that takes into account "background or appearance," with only 29 percent against. Lord Stevens, the former chief of Scotland Yard, endorses focusing on young Muslim men. The Guardian reports that "some EU countries, particularly France and the Netherlands, want to â€¦ introduce explicit checks on Muslim travelers." One politician in Wisconsin and two in New York state came out in favor of similar profiling. Fox News anchor Bill O'Reilly suggests that Muslim passengers ages 16 to 45 "all should be spoken with." Mike Gallagher, one of the most popular American radio talk-show hosts, wants "a Muslim-only [passenger] line" at airports. One author even proposes putting "Muslims on one plane and put the rest of us on a different one." The British Department for Transport reportedly seeks to introduce passenger profiling that includes taking religious background into account. News from British airports indicates that this has already begun - sometimes even by fellow passengers. Three conclusions emerge from this discussion. First, because Islamist terrorists are all Muslims, there does need to be a focus on Muslims. Second, such notions as "Muslim-only lines" at airports are infeasible; rather, intelligence must drive efforts to root out Muslims with an Islamist agenda. Third, the chances of Muslim-focused profiling being widely implemented remain negligible. As the same Wall Street Journal editorial notes: "the fact that we may have come within a whisker of losing 3,000 lives over the Atlantic still isn't preventing political correctness from getting in the way of smarter security." Noting the limited impact of losing 3,000 lives had in 2001 and building on my "education by murder" hypothesis that people wake up to the problem of radical Islam only when blood is flowing in the streets, I predict that effective profiling will only come into effect when a much larger number of Western lives, say 100,000, have been lost.