Complex sentence: Over the course of the war, more than 9,000 aircraft were ferried across the ocean and, by the end of the war, crossing the Atlantic had become a routine operation, presaging the inauguration of scheduled commercial air transport services after the war.
Split into simpler sentences: Over the course of the war, more than 9,000 aircraft were ferried across the ocean. By the end of the war, crossing the Atlantic had become a routine operation, presaging the inauguration of scheduled commercial air transport services after the war.