If bombing (manually at least) one can only use air units that have performed no other actions that turn; even 1% use will make that bomber unit unavailable for another mission. And even if that unit is not actually chosen to fly it can still get tagged as having flown, eg,
The only unit that flew was the two plane Stab/KG77 (one was damaged, hence only 1 is shown as ready on the screen above) - all other units were not flown that mission. Even so, they are tagged at 1%. (Just to be clear: nothing else has been done this turn, the ONLY thing that has been done is to bomb a unit explicitly picking Stab/KG77 as the only unit doing the bombing.)
However, if you fly III./KG77, then no other unit it tagged.
Intrigued, I ran multiple tests and the results are that if one flies a unit at the "top" of the list of units available at an airfield, ALL units below are shown to have flown 1%. If you fly them from the "bottom" of the list, however, only that unit it shown at greater than 0% (as it should be, of course, having flown).
Can't imagine this is WAD, but it's how it seems to work.
