It's not businessfirst, but you will get complimentary upgrades to "Business" (similar to domestic first) on Copa Airlines, if you connect in Panama City. There's no nonstop from SFO to PTY, so you'll have to double connect. (either SFO-IAH-PTY-EZE on Continental and Copa, or after october, SFO-LAX-PTY-EZE on United and Copa).

On the plus side, you can get paid business on Copa in the $1400-$1600 range, compared to the $4000 for CO BusinessFirst..