The dot EF command works great, and I appreciate the explanation on what unjoin is intended for. Thanks!
I get some crashes to white screen when requesting to join, but the problem is hit or miss. If I don't get into the B-17 of the other pilot on the first try, I just restart Aces High and try again. I carried an observer throughout the entire memorial flight of an hour and a half a few weeks ago, so I think the booting problem happens only sometimes.
We've had success with three different computers using the .join command with Aces High 2.19 patch 4. Two of them are Windows 7 64bit machines with 6GB ram, and one is a Vista 32 machine with 2GB of memory. All seem to be able to join at least 3 out of 4 tries and we don't seem to have troubles en route. I take a few seconds to click the "accept" button, and I don't know if a quick accept has detrimental effects, but you might try waiting a few seconds before clicking on "accept".