Japan's All Nippon Airways, ANA, said its fleet of 787 Dreamliners would remain grounded until at least the end of May, with no end in sight to woes for Boeing's next generation plane. The airline is cancelling 1,714 flights in April and May taking the total affected to more than 3,600 since the Dreamliner was grounded last month. Of the newly announced cancellations, 1,250 are domestic and 464 are international flights, including those bound for Seoul, Seattle and Frankfurt.ANA is Boeing's biggest Dreamliner customer so far, with 17 of the world's 50 operational 787s. The next-generation aircraft has suffered a series of glitches culminating in a global alert from the US Federal Aviation Administration after two incidents involving the battery packs. All operational 787s were grounded last month after smoke was detected mid-air on a flight in Japan.