Complex sentence: In December 2017, Japan Airlines invested $10 million, raising the company capital to $51 million: enough to build the XB-1 "Baby Boom" demonstrator and complete its testing, and to start early design work on the 55-seat airliner.
Split into simpler sentences: In December 2017, Japan Airlines invested $10 million, raising the company capital to $51 million. The company is funded enough to build and complete testing of the XB-1 "Baby Boom" demonstrator, and to start early design work on the 55-seat airliner.