On July 1, 1979 Western Airlines' service was extended eastward from Minneapolis / St. Paul to Milwaukee. The inaugural service was provided by two flights, one of which originated in Idaho Falls and used a Boeing 737 via Denver, Rapid City, Pierre, Sioux Falls and Minneapolis / St. Paul. The second flight, utilizing a Boeing 727, originated in San Francisco, operated nonstop to Minneapolis / St. Paul, then flew to Milwaukee. 

This cover was carried on the inaugural Western Airlines flight from Pierre, South Dakota to Milwaukee, Wisconsin (where it was backstamped) and is listed in The American Air Mail Catalogue as WA-D10E.

On September 9, 1986, the directors of Western Airlines and Delta Air Lines approved an $860 million purchase of Western Airlines by Delta Airlines. On October 3, 1986 the Justice Department’s antitrust division announced that it would not oppose the acquisition. On October 23, 1986 the Department of Transportation gave tentative approval to the merger. Final government approval was made on December 12, 1986 whereupon Delta Airlines completed its acquisition of Western Airlines, making Western Airlines a wholly owned subsidiary of the Atlanta-based carrier. The carriers continued operating as separate airlines until April 1, 1987, when Western Airlines’ operations were combined with Delta Airlines’ operations. Western Airlines, which had commenced operations in 1926, ceased to exist as of April 1, 1987.