My suggestion is that you put a "Spawn Area" over an airbase of choice and via properties controls what plane you/him will be able to choose, at the same tab you will be able to set number of planes available - that will be your possible respawns more or less.
Host by selecting Multiplayer-Server-Pick the mission-Start Battle-click the flag (choose side)-select the "white" airbase (your spawn area)-click on the plane to choose another plane if available-click "create" to spawn into the airbase parking area (if you set the spawn area correctly in editor).
Your mate will select Multiplayer-Client-select your server-optionally type in password-and then do the same procedure as you did after "Start Battle".
When you crash or just wants to ditch the plane (standing at the and of the runway with nose down - been there done that haha) press escape, select flag/side and confirm leaving plane and repeat above.
Good luck getting him up and running, having a very hard time to get "my ePilots" to spend time in Dover makes the above process rather deadly, but it works.
Edit: Oh and for the coop situation, make the enemy flight "script spawn" and let them loose when you or your mate enters a trigger - that way you can run full CEM and hassling around on ground without any stress due to mission design enemy flights - RAMP start will in effect be the new pre-coop-chat-and-have-a-laugh that is the today missing coop interface of 1946.
If all above to total overkill for you I can slap together a mission for you guys to have a look at and adjust as preferred.
(or just rip apart my "Italian Visit" in this training pack:
http://odenhouse.servegame.com/DoverTraining.7z I think that one has the basics you're looking for, just no enemies)