Atis Lielmanis was born on January 2, 1939, in Latvia, and immigrated to the United States from a displaced person's camp with his family from Germany in November 1950. He enlisted in the Aviation Cadet Program of the U.S. Air Force for Navigator Training on September 22, 1958, and was commissioned a 2d Lt and awarded his navigator wings on November 4, 1959. Lt Lielmanis served as a transport navigator before joining the 602nd Fighter Squadron as a B-26 Invader navigator in April 1963. He deployed to Southeast Asia in July 1963, and was killed in action while serving with the 1st Air Commando Squadron at Bien Hoa AB, South Vietnam, on November 24, 1963. Atis Lielmanis was buried at the Union Cemetery in Quakertown, Pennsylvania.

His Air Force Cross Citation reads:

The President of the United States of America, authorized by Title 10, Section 8742, United States Code, awards the Air Force Cross to First Lieutenant Atis K. Lielmanis for extraordinary heroism in military operations against an opposing armed force as an Advisor-Navigator of a B- 26B aircraft on 24 November 1963. On that date, Lieutenant Lielmanis voluntarily exposed himself during a low level flight over hidden Viet Cong machine gun installations. Their fire badly damaged the aircraft, and it crashed, but this revealed the Viet co0ng positions and resulted in their destruction by cover aircraft. Through his extraordinary heroism, superb airmanship, and aggressiveness in the face of hostile forces, First Lieutenant Lielmanis reflected the highest credit upon himself and the United States Air Force.