Don learned about glacial landings from his father-in-law, Bob Reeve, who was himself a famous Alaskan pilot and founder of Reeve Aleutian Airways, and also worked with Bradford Washburn. Sheldon and Washburn would work together for over fifteen years.
What I enjoyed most was that he so unselfishly offered his services to those in need. There are several accounts of him making an unheard of flight manuever in order to rescue climbers, ship wrecked boaters or lost hunters. Almost every effort to climb the mountain ranges around Talkeetna including Denali (Mt. McKinley) during the period of 1940 - 1970 likely involved this world renowned bush pilot. Sheldon was heralded for his amazing ability to land on the sides of mountains. Most of his career was spent flying people to some of the most remote locations in Alaska. (Source)