He was an honors student at Bay View High School, where he graduated in the class of 1939, and attended the University of Wisconsin.
Kleffen was the co-pilot of B-24J #42-78685, assigned to the 10th Air Force, 7th Bombardment Group, 492nd Bombardment Squadron. They were flying a cargo of fuel from Tezpur India over the Himalayas to Kunming China when they disappeared.
Because his body was not recovered, he is memorialized on the Tablets of the Missing.
Kleffen is also memorialized in Woodlawn Cemetery in Milwaukee Wisconsin.
Gravesite Details Entered the service from Wisconsin.