Do you know how you go about that? Do you call the mileage program of the airline and tell them you have an account with the other?
I have enough United miles from my 2 trips to China for a ticket but there was nowhere I would fly stateside on them from Cleveland. However, I always fly Continental from here.
No, you book through the program for which you have the points, but they can put you on any of the airlines.
For example, I have my points with Air Canada (also part of Star Alliance), their program is Aeroplan. Let's say I want to fly to Capetown. I go to the Aeroplan site (or call Aeroplan) and look for flights from home to Capetown. Air Canada doesn't fly into Cape Town, but I can get flights via South African Airlines (also part of the alliance).
So, I am using Aeroplan points and the Aeroplan website (or call centre) but will be flying on South African Airlines.
Sometimes, you are forced to use the call centre (rather than the website), since not all of the flights on the other airlines are loaded onto the websites.
Star Alliance has a good website (
www.staralliance.com), you cannot book anything through them, but it gives you the routing between two cities on any of the airlines (or a combination thereof). This is useful since, as I said, not all flights from all the airlines are loaded into each individual website and it saves checking all the airlines. With Capetown, it is obvoius that South African Airlines will fly there, but maybe United, Continental, or BMI do as well - the Star Alliance website would tell you.