The only way I can see is to assign airplanes to your pilot before each mission from drop-down menu list.
That will be a great new add, Jara!
I vote for all planes in the pilot's country to be on the pick list. Because we don't have instant transfers in WOFF, we've got to run 3 to 5 fast missions under time compression to switch a pilot from say, a DFW squad to a Hannover squad. Now I can just switch my squad out to Hannovers in your ME in a matter of minutes if I'm in the mood to fly Hannovers instead of DFWs that night.
Or, I've just flown my Camel to a friendly airfield on an errand, and I've decided to accompany an RE8 raid on my way back home. I change out my RE8 for a Camel, and I'm there! I find that I need to fly into Bray Dunes quite frequently on errands. And I often accompany an outbound RE8 raid on the way home!