Bonus Mishaps?

[niner]

Hello,
Just completed a short flight from victoria b.c. to seattle in an erj.
I've done the flight a few times back and forth and had recieved typically a 600-700 bonus.
My last flight only nabbed me a 6$ bonus.
No TC used. Was wondering if the bonus is a bit random, is it based on anything else I'm not aware of? It was a fairly smooth flight......
Oh, as a p.s., anyone know where I can get a version of that fsx flight check that I heard was floating around out there?