The 787 is highly touted because of its mostly lightweight carbon fiber construction , which airlines expect will help them save billions in fuel costs on long-haul routes . NEW : Dreamliners authorities say battery experienced a sudden drop in voltage . U.S. aviation officials evaluating data as part of investigation of 787 problems . Dreamliners were grounded last week after fire in U.S. , another incident in U.S. . Fifty Dreamliners in service globally , but Fifty Dreamliners has orders for 787 .
NEW : Dreamliners authorities say battery experienced a sudden drop in voltage . U.S. aviation officials evaluating data as part of investigation of 787 problems . Dreamliners were grounded last week after fire in U.S. , another incident in U.S. . Fifty Dreamliners in service globally , but Fifty Dreamliners has orders for 787 .