Complex sentence: The squadron is one of the oldest in the United States Air Force, its origins date to 16 June 1917, when the 18th Aero Squadron was organized at Rockwell Field, San Diego, California.
Split into simpler sentences: The squadron is one of the oldest in the USAF. Its origins date to 16 June 1917, when the 18th Aero Squadron was organized at Rockwell Field, San Diego, California.