Karl Schmolsmire Day (May 30, 1896 – January 19, 1973) was a naval aviator of the United States Marine Corps Reserve who rose to the rank of Lieutenant General.

A veteran of World War I, Day served with Northern Bombing Group on the Belgian front and awarded the Navy Cross, the United States military's second-highest decoration credited for valor in combat.

[1] Day sailed to France in July 1918 as a recently promoted captain and member of Squadron C, First Marine Aviation Force, Northern Bombing Group.

Day took part in the flight mail duties in 1933 and was forced to bail out of a disabled airplane and thus became member of the Caterpillar Club.

[1] After the organization of first Marine Reserve Aviation unit in the New York area at Floyd Bennett Field in 1935, Day was promoted to the rank of major and appointed as commanding officer of the squadron.

He found Navy and Marine Corps pilots lacking in knowledge of instrument flying, which was basic to bad weather operations.

He was appointed Peleliu Air Base Commander and was responsible for the operation of the airfield, which became the principal staging area for the Philippine Campaign.

[1] Day was promoted to the rank of reserve brigadier general in 1948 and assumed command of the Volunteer Training Unit in New York City.