Complex sentence: The CSeries aircraft contain 70% advanced materials comprising 46% composite materials and 24% aluminium-lithium which allows for a 15% lower seat-mile cost and a significant reduction in maintenance costs.
Split into simpler sentences: The CSeries aircraft contain 70% advanced materials comprising 46% composite materials and 24% aluminium-lithium. Bombardier announced in total 15% lower seat-mile cost and a significant reduction in maintenance costs.