Tampa, Florida and graduated from the University of Tampa with a B.S. degree in 1941. He enlisted as a flying cadet in 1941 and was commissioned and awarded his pilot's wings in April, 1942. He flew 150 combat missions in the China-Burma-India Theater (C.B.I.) of World War II and later in the Korean conflict. Col. Upson was a command pilot and awarded the Distinguished Flying Cross with cluster, Air Medal with two clusters, and the Bronze Star medal. He married Mary Elizabeth "Betty" Standau, also of Tampa, in 1942 and had four children. Linus retired from the Air Force in 1966, settled in Northridge, CA and started a second career with Hughes Aircraft Company. When his wife Betty passed away in 2009, he moved to San Diego where he lived until his passing on May 2, 2014.

Upson flew with the 80th Fighter Group – consisting of the 88th, 89th, and 90th Fighter Squadrons – in the C.B.I. campaign. Labeled the “Burma Banshees,” he was stationed in Burma to attack the Japanese forces. They assisted India with the Japanese sweep. They trained in Republic P-47 Thunderbolts but flew combat missions in the Curtiss P-40N. After two years in combat, the squadron was removed from duty.