Hello Flyertalk, this is my first post, so, uh, go easy on me.

I've been reading that people would use Amtrak Guest Rewards to convert Onepass miles into Mileage Plus miles, so I figured it was possible to convert Onepass miles to Amtrak points. I've been searching on both releveant websites, and while it seems I can use Amtrak points for Continental travel, I can't do it the other way around? Am I wrong? Are there any other ways to use airline miles (besides Midwest) for amtrak travel?

Thanks for your responses.