PITTSBURG, Kan. — Early Friday afternoon, the sky above Pittsburg was host to a trio of old veterans, the oldest of which served during the Second World War as a trainer for countless American pilots. Christened “Grandpa’s Plane,” the Stearman biplane was built in Wichita in 1940, and served as a training aircraft in Missouri, Arizona, and California during the war. It was purchased in 1946 by William Fisher and has been in his family for four generations.