Also, since when is "profit" a bad word? Using the means of free trade to improve one's situation is the foundation of civilization. People act as if the quest for profit turns you into some sort of Scrooge McDuck figure who counts dollars and stashes money away never to be seen again.
Besides that as the poster above you mentioned, Blackwater is what happens when you trust the worst sorts of persons to protect the nation.
What went wrong during 9/11 was that passengers assumed that a hijacking was a financially-motivated detour, rather than a political/religious attack on our ways of life (and prior to that day, there was no reason to assume otherwise). As such, there was very little resistance to the hijackers as people didn't want to get cut by a relatively small knife. Had they had even the faintest idea that failure to resist could have resulted in what happened, you can say with 100% confidence that things would have gone down differently.
Basically, that trick was good once and once only, regardless of the change in security policy that it brought about. And let's face it - only an idiot would try that again; there are targets with far higher value (and probably much more exploitable security flaws) if someone wanted to send a message again.
Specifically, the large gatherings of tightly-clustered people waiting at a security checkpoint are much more vulnerable than any plane full of passengers.
Given the odds of actually needing them vs. the continued inconvenience of travel, I'll go with the convenience every time.