Complex sentence: The JT9D was developed as part of the design phase of the C-5 Galaxy, a contract was awarded to Pratt & Whitney to study the type of large engine needed but the production contract was eventually awarded to General Electric and their TF39 turbofan.
Split into simpler sentences: The JT9D was developed as part of the design phase of the C-5 Galaxy. A contract was awarded to Pratt & Whitney to study the type of large engine needed, but the production contract was eventually awarded to General Electric and their TF39 turbofan.