Delta Airlines: Changes to frequent flyer redemption's effective December 1st. "SkyChoice Award Ticket Reservations will no longer be available on every Delta flight in which a seat is available for sale. SkyChoice Award Ticket Reservations will continue to be available on most Delta flights, but seats will be limited and possibly unavailable on some flights."

Translation: Under the current policy, a "SkySaver" award redemption for travel in the U.S is 25,000 miles, subject to capacity control (hard to find an available seat). You still had the option of spending 50,000 miles though "SkyChoice" and you could choose any seat on any flight. New policy states "SkyChoice" will now also be capacity controlled (you can no longer have any seat, any flight), but you will have more options than a Saver ticket.

Alaska Airlines: Effective April 1, 2008. Mile balances in your Alaska Air frequent flyer account will expire after 2 years of no activity (down from the existing 3 year requirement).