Title really says it mostly..
http://www.frequentflier.com/blog/new-at-american-bidding-for-upgrades/Effective immediately, would-be upgraders can reality-test their aspirations by bidding for upgrades on American flights. For now, the bidding is offered only in “a limited set of markets,” but it’s likely to be expanded systemwide once the system and procedures have proven themselves.
Upgrades are available for bids six days prior to a flight’s departure. For eligible flights, passengers enter their bids and payment information on the airline’s dedicated bidding webpage. Successful bidders will be notified by email at least 24 hours before the flight.
Although bidders pay a premium to fly in a premium cabin, they only earn miles for the class of service originally purchased.
Displaced Elite Upgrades?
American takes pains to reassure worried elites that their upgrades will be protected. “AAdvantage elite status members (Gold, Platinum and Executive Platinum members) should continue to request 500-mile upgrades (complimentary or purchased) as normal. This option is offered to passengers who aren’t able to use 500-mile upgrades, either because they aren’t AAdvantage members, or because they are traveling on fares that are not eligible. Rest assured that elite status member upgrade requests will continue to be given priority and will not be impacted by this program.”
