Crap. I'm only an occasional traveler. Just read the microprint on the vouchers and there it is "Certificates are not valid for travel on Star AllianceTM flights or United-marketed flights operated by other airlines."

Never the less, your trick for searching award travel brought up the flights and the option to buy them at Copa's price. I at least I get the United Miles instead of Copa's Miles.

Thanks for the fast replies, you guys are a wealth of information.