Boeing Co on Wednesday reported a second-quarter adjusted loss due to charges related to its troubled defense and space unit, as the U.S. planemaker grapples with labor constraints and supply-chain disruptions.

Boeing posted a core loss of 37 cents per share in the quarter through June compared with a year-ago profit of 40 cents per share.

The planemaker, however, remains on track to generate free cash flow this year and is in the "final stages" of preparing to restart 787 Dreamliner deliveries, Chief Executive Dave Calhoun said in a letter to employees. (Reporting by Abhijith Ganapavaram in Bengaluru and Rajesh Kumar Singh in Chicago; Editing by Saumyadeb Chakrabarty)