I admit that I'm an old fart, but when I was on my first cruise and we were doing flex-deck ops (round the clock ops for 24-36 hours to test our wartime capability), you would fly, catch a couple hours of rest/sleep, fly again, repeat, till the powers that be determined we could operate at a tempo sufficient to win the battle. There was never any mention of "crew rest". Was it safe? By today's standards, undoubtedly not. But we never lost anyone. Did we question the legitimacy of this type of ops? Of course, but the cold war was still going on and everyone figured if the balloon ever went up, we had to be prepared. It wasn't until I got to the "Show" that I first heard of "crew rest".