There has been no formal announcement, but a note in the partners chart for Delta’s SkyMiles program says that Delta’s mileage partnership with Midwest Airlines will terminate on June 7, 2010. Delta inherited the Midwest alliance from Northwest, which had once been a part-owner of the Milwaukee-based carrier. Midwest is now owned by Republic Airways Holdings, which also owns Frontier Airlines and several regional carriers. Republic has been working to integrate Midwest and Frontier, and has already brought their frequent flyer programs together. Republic is reportedly studying plans to unite the two airlines under a single brand in order to facilitate marketing. News of those plans recently brought protestors onto the streets of Denver, urging Republic not to drop Frontier’s iconic animal mascots, which are painted on the tails of all its aircraft.