Washington ( CNN ) -- United Airlines plans to resume flying the 787 Dreamliner in May , the carrier told CNN in anticipation of regulatory approval of Boeing 's remedy for battery problems that forced the jetliner 's worldwide grounding . While United is the only U.S. carrier that flies the wide body , a signal from the world 's biggest carrier indicates that others are also likely making plans to resume service in coming weeks . For the first time in months , it also indicates a clear time line for Boeing to return the aggressively promoted but troubled jetliner to the skies after it was grounded by regulatory authorities globally in January . United said it plans to start flying 787 again on May 31 . Final battery test on Dreamliner 'straightforward ' `` We are in the process of formulating our domestic flying plans and will be making additional schedule changes as we gain visibility to the time line for certification and modification work , '' Christen David , an airline spokeswoman said . United said it will fly the plane on both domestic and international routes . Boeing modified the 787 's lithium-ion battery system after fires in Boston and in Japan prompted aviation authorities globally to ground it . It completed new test flights last week . The Federal Aviation Administration ( FAA ) will review the test data and must sign off on the redesign . Transportation Secretary Ray LaHood has said the Dreamliner will not be allowed back in service until Boeing proves the new design is safe . Boeing has placed a huge bet on the lightweight , mostly carbon-composite jetliner . Only 50 Dreamliners were flying worldwide at the time of its grounding , but the world 's largest aircraft manufacturer has orders for several hundred in the pipeline .
United Airlines is only U.S. carrier that flies the 787 ; 50 in service worldwide . The 787 was grounded in January after two battery fires in Boston and Japan . The Federal Aviation Administration must still sign off on Boeing 's battery redesign .