As of June 7, 2010, Delta SkyMiles and Midwest Miles will no longer partner. Delta said it ended the partnership because of “a change in Midwest Airlines’ ownership and business strategy.” Delta and Midwest also are ending a codeshare agreement.

Bottom line: This was a rather short-lived partnership of only about a year and came about when Delta merged with Northwest (Midwest was a Northwest partner). And at one time, there were rumors that Delta might acquire Midwest but that all ended when Republic Airways Holdings Inc. bought Midwest in the summer of 2009.