In order to spawn Mission 10's ace, you have to quickly locate and destroy all nine camouflaged anti-air weapons. They won’t appear in your map until you get near them. You can follow the smoke trails but unless you have the general idea of their locations, it will be challenging to find them all without some sort of intel or guide. Worry not since you just need to refer to the image below for the SAM sites’ general locations.
If there are SAM sites are accompanied with AA guns and you don’t have enough time to destroy all of them in a single fly-by, prioritize taking out the AA guns first. You’ll be starting off in the northeast corner of the map so work your way around the SAM sites southward then to the west. This flight pattern can help:
You can also refer to the screenshots of the individual SAM sites as they appear in order in the diagram above. After destroying all SAM sites continue with the mission until the escort is near the allied field. LOUVETEAU will be part of the enemy squadron that will arrive from the eastern side of the map. To be safe, this has to be done (presumably) within two minutes since the mission started (over 9:00 remaining on the timer)