I did a search and couldn't find this specific issue covered, so here goes.
Let's say I want to keep a relatively clean directives list so everything shows up as it should when all hell breaks loose, and thus I want to consolidate all my "destroy <wing>" directives into "Destroy all fighters" and a second one for "Destroy all bombers."
I THOUGHT it would be easy, that I could use the ship-type-destroyed SEXP and set it to 100% of fighters and 100% bombers. Ha. No. That calculates fighters and bombers present in the mission. If you clear them out, even though waves will respawn later, that directive goes to true. Simply marvelous.
Then I tried using is-destroyed-delay, and adding all the fighter wings and all the bomber wings. Problem is, because they enter the mission at various times, the directive doesn't show up until every wing has arrived. That didn't work either.
So them, is desperation, I tried dummy events. No dice there either - same effect as above.
So - is it possible to add a directive that tells you to destroy all of a certain kind of ship, even before all of those ships enter the mission, and doesn't complete until all respawns have ceased? Or is there another way to do this?