ORIGINAL: USS America
Unless you specify a percentage to rest, the remaining pilots/planes are on standby to launch what ever primary mission type you have selected for the squadron. Even if that mission is Naval Search and you set 50% to Search, the other 50% are not stood down, and sleeping, etc, but are "ready" to launch. There is much more benefit for reducing fatigue and morale problems if you specifically order a percentage to rest.
This is the approach I have used in the past, and the approach that would seem to make the most sense. However, with this approach I have not seen the number of missions spread evenly among the pilots.
Take a squadron with a Training mission set at 30% Train/70% Rest over several turns. In my experience, the 30% of pilots who flew the mission on the first turn are largely the same 30% of pilots who fly missions on subsequent turns. The majority of the remaining pilots (i.e., those who rested on the first turn) do not fly missions on subsequent turns. I do not see an even spread of missions among all of the pilots over several turns. Some pilots fly 12 missions, while other pilots fly 0 missions.
Recently, I have started to set the squadron at 30% Train while leaving the other patrol levels at 0%. With that setting, I have seen all of the pilots rotate through flying missions. The number of missions, experience increase and fatigue seem to be spread more evenly among the pilots with this approach.
I have not done an in-depth study of this by any means, so I can't say with certainty that this is the result for all percentage settings or all types of missions. It is just what I have seen, especially on Training, Naval Search, ASW and CAP missions.
I use "Rest" to limit the number of pilots/planes that will fly a mission on a particular turn. If I want a naval strike by only half the squadron and I want the remaining half to not fly at all, I will set the squadron at 50% Rest.
Has anyone else used this approach or should I go back to setting the squadron to at least some percentage of rest?