Complex sentence: Upper Heyford in Oxfordshire is a village at the foot of Royal Air Force RAF Upper Heyford that was the site of the USAF 20th Tactical Fighter Wing which flew the F-111 and EF-111 aircraft up till the early ninties.
Split into simpler sentences: Upper Heyford in Oxfordshire is a village at the foot of Royal Air Force RAF Upper Heyford that was the site of the USAF 20th Tactical Fighter Wing. The wing flew the F-111 and EF-111 aircraft up till the early ninties.