I've been trying to come up with something, but I can't decide on anything. The only thing that I've really decided is to have Rainbow Dash as one of the main characters of the story.

Gilda and Dash were childhood friends, war breaks out between Griffonstone and Equestria, Dash and Gilda are squadron leaders on opposite sides of the trenches.

The war on the ground degenerates into stalemate and atrocities, but the knights of the sky remain chivalrous to the end.

7473241

big Mac becomes a noble, with the noble title of baron, thanks to the fact that his apples are the best in equestria, he is later called to arms, where he learns to use flying machines and the rest is history ;)

7473241
It depends if you're talking about THE Red Baron, or just a Red Baron-alike. If it's the former, there are plenty of "IRL humans suddenly popped into Equestria for no reason" stories, so I'd assume a story with THE Baron would be much the same. By contrast, a story with a Baron-alike would be similar to Sock Puppet's idea, in that Rainbow Dash is squaring off with an enemy ace in a WWI-style dogfight (whether or not it's Gilda like Sock Puppet suggested, or an OC is up to you)

I think the problem with writing a story about Richthofen is that, beyond his impressive kill numbers, he didn't really have that interesting a personality - he was just another Prussian aristocrat.

7473325
He Like dogs that counts

Well, I would say a Griffon War or insurrection.
The Red Baron would be charismatic and gentlemanly but also intimidating and ruthless.
Maybe play it quite close to the chest like the 'Scarlet Duke' or the 'Crimson Count'.
Or maybe even 'The Cardinal' if he resembles the bird (Although that's a bit small so maybe it would just be a nickname...unless you want to make him out to be a sort of Napoleon-ish character as well)

7473325
Well that in itself is interesting. As could you imagine all the trouble he could get himself into. Especially due to his cultural values.