Complex sentence: He was subsequently certified to fly both single and multi-engined aircraft between 225--1500 horsepower, and began to fly for Pan American World Airways before being discharged from the Army Air Force in July 1945.
Split into simpler sentences: He was subsequently certified to fly both single and multi-engined aircraft between 225 and 1500 horsepower. He began to fly for Pan American World Airways before being discharged from the Army Air Force in July 1945.