Earlier quoted context omitted.
This is naive. Why would you assume the same number of successful attacks on air travel would occur without the security? You can't argue that the current system hasn't done well, it has performed fantastically, based on the number of successful attacks within the US. That said, they need a lot more screeners, and to be much more polite. And get rid of incompetent management.
How many attacks were stopped by the TSA? Directly: 0. Hell, they're 0/2 on known attempts (the Shoe Bomber in 2001 and Northwest Airlines Flight 253 in 2009), both thwarted instead by passengers and crew. Indirectly? (E.g., how many attacks weren't planned because of the TSA that would have been planned and executed otherwise?) Very hard to say. Have law enforcement officials seen an uptick in other terror channels…
No one here is familiar with the concept of "deterrence", apparently.