Problem in Multiplayer - Friend can't select a plane
 

So I've been enjoying Cliffs of Dover for a long time, knew there was multiplayer, and convinced a friend to buy it so we could play together. We tried to do so recently and ran into problems.

Once I got a server up (he had to connect directly to my IP and port as opposed to just finding it in the list) I picked one of the stock missions and selected start battle. When my friend joined in he could see the list of planes but couldn't fly any of them because they all said WPF.unavailable.

Looking around I see this to mean that he can't spawn into a plane more than 20 km away. But that doesn't make sense because there were only six spitfires, all flying in formation, well closer than 20 km.

What are we doing wrong? We just want to fly missions together. Why is this so difficult?

You and your friend are more than welcome to jump on the ATAG server.
Each can jump into a plane and fly together there.

While that's great and we may resort to doing so, I'd like to be able to get it working as is so we can run our own game together.

Check out realism settings if plane switching, etc, etc. are allowed.

The 100% working way is to select a spawn point on the map and spawn a new plane.

You may also try the coop-script by Banks.