Complex sentence: Internally the hull was divided into two decks linked by steps and entered by doors, aft of the wing, to each side of the upper deck which was reserved for the crew, with sleeping quarters forward under the cockpits and access to most control systems.
Split into simpler sentences: Internally the hull was divided into two decks linked by steps and entered by doors aft of the wing, one to each side of the upper deck. This was reserved for the crew, with sleeping quarters forward under the cockpits and access to most control systems.