Mmhhh. I think the OPs sentence is misleading. „… teaching them how to fly …“. Yes you have to be a certified instructor if that sentence is meant literally.
If however you teach or offer coaching of using MSFS (flight sim or game …) you don’t need the certificate (in some sense YouTuber showing the sim are also doing this and they indirectly get money for it).
However the EULA would be my main concern about monetizing a licensed product.
Maybe better try it for free first (or for a coffee) and „test“ the market. 