 In the 1930s, Kinner was the owner of Security National Aircraft Corporation at Downey Field, now Downey Studios.Kinner died on July 4, 1957 in California, the "Washington Post" noted, "Winfield Bertrum Kinner, 74, pioneer aircraft manufacturer and designer, died late Thursday in a Long Beach hospital ... ".He was buried in the Portal of Folded Wings Shrine to Aviation with other aviation pioneers in Valhalla Memorial Park Cemetery.