Complex sentence: Some military air forces combine use of civilian airports with the hosting of military units although military aircraft usually use substantially different support equipment, and require facilities sufficiently isolated from civilian operations and their large and concentrated groups due to aviation safety of weapon ordnance they use.
Split into simpler sentences: Some military air forces combine use of civilian airports with the hosting of military units. However, military aircraft usually use substantially different support equipment, and require facilities sufficiently isolated from civilian operations due to issues of aviation safety involving the weapon ordnance they use.