But the increase in air transportation security has had an impact. Fewer people are flying. The airlines don't like to discuss this, but customer satisfaction, and travel, surveys show that people, especially business flyers (the most lucrative kind of passengers) are flying less. The reason is the increased, and seemingly irrational, screening methods. These antics also have a negative effect on the security personnel. There are now 2,100 air marshals (versus 33 on September 11, 2001), and half of them are unavailable (all or part of the time) because of health issues caused by too much time in the air. The air marshals work a heavy schedule, averaging twenty flights a week. Not that it's doing much good. Until this Summer, air marshals had to fly wearing suits, despite the fact that most passengers go casual. Thus the air marshals stick out, giving any potential bad guys an easy way to identify, and take down, the law.
While the air marshals can now blend in, most flight personnel realize that it is more likely that a mob of enraged passengers is the best defense against any hijackers. Air marshals only fly a small (classified) number of flight, there are many passengers on each flight who are willing to risk all to take down hijackers. The airlines don't like to encourage that sort of thing, but there is it. And the terrorists know it as well, which is why they stay away from air transportation.
Efforts to prevent any more Islamic terror attacks on American passenger aircraft have, on the face of it, been successful. Increased passenger screening, and heavy use of air marshals, appears to be the primary reason for the prevention of terrorist attacks in the air. Or has it? Aviation in the rest of the world has not been nearly as energetic as the United States, and they have also been free of terrorist attacks. In fact, the Islamic terrorists have been attacking other modes of transportation (as in Spanish trains and British buses and subways). In fact, interrogations, and captured terrorist documents and the like, have indicated this shift in target emphasis.