Q. I just got an e-mail alert from Virgin informing me that I can exchange miles from other airlines' programs for more "Elevate points."  This would be great if it were for United since my primary mileage program is with Mileage Plus.  I do take about a dozen non-Star Alliance trips a year and rack up a handful of points on random airline programs that never amount to anything before they expire.  Do you know if Mileage Plus supports some sort of mileage exchange program as well?  What about with other Star Alliance partner airlines?  For instance I have about 12,000 miles on US Airways and I know they are also Star Alliance.  Could I shift those over to my Mileage Plus account?

A. We put this one to our friend and miles expert, Tim Winship, publisher of FrequentFlier.com. Here's what he had to say on the matter:

Through Points.com, you can now exchange points from other participating programs for points in Virgin American's Elevate program. There's no fee for the exchanges, but you'll end up with far fewer miles after the conversion.
 
You can also trade miles and points through Points.com. The exchange rate is market-based, whatever the parties agree to.  But there is a trading fee.
 
With very few exceptions, exchanging miles among programs is either unduly expensive or results in a wildly unfavorable exchange ratio. It generally makes sense in two situations:

1. Converting just a few thousand miles, to bring your account balance up to an award threshold.
2. Converting "orphan miles" from a program you don't actively participate in into miles in an active program.

Exchanging miles among airlines that partner in alliances (i.e., United and US Airways, which co-participate in the Star Alliance) is no different than exchanging among unrelated airlines.