Complex sentence: In 1943, at the height of World War II, Gainesville contributed to the war effort by leasing the airport to the US government for $1.00, who used it as a Naval Air Station for training purposes.
Split into simpler sentences: In 1943, at the height of World War II, Gainesville contributed to the war effort by leasing the airport to the US government for $1.00. The military used it as a Naval Air Station for training purposes.