I changed where the bomb skill was assigned, and removed the Zeppelin Barrage skill, and moved some of the others (in the Xbox version).
IIRC, I changed them back too, but in the pc version they went coming back again, removing one more time my choices.
But as I was upset (I already don't like those console-like hurrying protecting missions), I didn't bother much with this problem, maybe I did not insist.
Maybe, often in pc games, key-pad is not used, and I use it. Maybe the game was not made for the key-pad and that's why I couldn't play well? I don't remember.
Without this ending, this game would be in my top 20 list (at least, maybe top 10) of pc games
(It was, before I had seen this end. I think I even registered this forum just to thank you, at first).
EDIT: Okay, seeing my 1st mail, I buy again the game(s) on GOG. I hope you'll make something for this game's end.