Turning Point (Possible spoilers!)

I have a different view of the movie (and I talk here about the movie, not the novel). My understanding is that the issue is understanding what's really going on, from Heller's point of view (seeing Yossarian as a stand-in for Heller).

At first, Yossarian says the Germans are trying to kill him. He tries to get out of flying missions. Then Colonel Cathcart keeps raising the number of missions Yossarian has to fly, so Yossarian realizes that he's in as much danger from his commanding officer as he is from the Germans. Then Yossarian realizes that the military is in the pocket of the capitalists, personified by Minderbinder. It's not just the Germans and his commander who are trying to kill him, it's the people making money off the war. And the capitalists and military have become one (the military-industrial complex Eisenhower complained about).

I think this is emphatically stated in what I think is the climax of the movie:
Nately has been killed in the raid staged by Minderbinder on behalf of the Germans, and Yossarian is complaining to Minderbinder, who is standing in his staff car. Minderbinder says Nately's shares will make his heirs rich. Yossarian says Nately's heirs are his parents and they're already rich. Minderbinder says, Then they'll understand.

I think Yossarian realizes that they are out to get him: the Germans, the USAAF, the companies running America. This is when he realizes he can only run away. There is no other choice. In my view, Yossarian is sane the entire time, but he eventually comes to the realization that there is no enemy, no patriotism; there is only profit.