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It is painfully obvious, what went... well, if not wrong, then I would say... amiss.

No German side campaign (not even as an expansion - why the heck not? - given all the circumstances, that would actually suit the KotS style better).

And practically no allied planes to support you or the entire war effort... (Amiga version had something circling around the airfield, but nothing more).

No wonder the Red Baron was received much better, as it had both of these omissions rectified (though there were many other features missing - it had the Zeppelins, though) and I always felt, that Red Baron II/3D was as much KotS II as it was RB II (similarities between RB II and KotS are difficult to ignore - now, they are logical, given the same topic being covered, but anyway).

Ok, just random thinking out loud to fill this board... :-)
Well there has to be the better title, if KotS would have the same features as Red Baron they would be clones. :^)
Also, Microprose was putting out flightsim after flightsim in those days, some of which were very good while others were lacking.
In the game's manual's Designer Notes section, Jeff Briggs explains they didn't have the time and much less ressource to inclue a German campaign. They didn't want to simply mirror the French/English one.

There are lot of allied planes supporting you, but sadly, the Steam version (and I assume, the GOG version), published by Retroism, isn't the patched to Ver.2 one! That “little” patch introduced allied patrols(!), amongst other things, bringing the field to life and giving you much needed support. You can find the patch at the Patches Scrolls ( Why this version of the game isn't patched is beyond understanding.

To me, although it lacks the weather effects and the flight model of Red Baron, Knights of the Sky is much more atmospheric and overall my favourite game of the two. It combines perfectly arcade and simulation (I love how distinctive every planes are, however irrealistic that sometimes may be) and evokes neatly the romanced view of the period (in the same way that Microprose did before with Pirates, if you wish).
Got the game today and just want to tell that
I think Rev 2 is already included in the latest installer.
There is a READ.ME of the "Rev 2 patch installer" in the game directory.
I have also encoutered allied planes fighting germans in the skies.
So, it looks like there is no reason to search for the patch.