MSFS format for writing import/exporter

I would like to write an importer/exporter for MSFS files into my modeler. Where can I find the spec/file format?
Any tips you can give me?
My apologies if this has been answered ad nauseum. My connection is so crappy that a search seems to take days.
Cheers,
-lyw
Any tips you can give me?
My apologies if this has been answered ad nauseum. My connection is so crappy that a search seems to take days.
Cheers,
-lyw