Complex sentence: At the end of 2016 five National Security Cutters are in active service, and an additional four NSCs are under construction at Ingalls Shipbuilding (NSCs "Hamilton", "James", and "Munro").
Split into simpler sentences: At the end of 2016 five National Security Cutters are in active service. An additional four NSCs are under construction at Ingalls Shipbuilding (NSCs "Hamilton", "James", and "Munro").