Complex sentence: As a child, he had always dreamed of becoming a pilot and after he graduated from high school, he entered the University of Puerto Rico at Mayaguez where he earned his Bachelors Degree in Aeronautical Engineering, he was also a member of the campus ROTC program.
Split into simpler sentences: As a child, he had always dreamed of becoming a pilot someday. After he graduated from high school, he entered the University of Puerto Rico at Mayaguez where he earned his Bachelors Degree in Aeronautical Engineering, he was also a member of the campus ROTC program.