Complex sentence: The Army Aviation Group was originally formed during the Bangladesh Liberation War of 1971, when 3,000 personnel left Pakistan Air Force and decided to raise an aviation wing of Bangladesh Liberation Force, both Army Aviation Group and Bangladesh Air Force was raised by those personnel.
Split into simpler sentences: The Army Aviation Group was originally formed during the Bangladesh Liberation War of 1971, when 3,000 personnel left Pakistan Air Force and decided to raise an aviation wing of Bangladesh Liberation Force. Both the Army Aviation Group and Bangladesh Air Force was raised by those personnel.