New threats to air travel have produced new strategies and technologies against explosives in shoes and carry-on liquids--even in underwear. But some passengers resent the new body-scanners in 68 American airports, and the pat-down hand search is also provoking a backlash. It’s invasive; it’s embarrassing Does it violate the 4th Amendment? Will it really work? Has the Transportation Security Administration gone too far? Is the real key to security the intelligence gathered before anyone gets to the airport?