Japan\'s two major airlines said Wednesday they had replaced a number of batteries in their Dreamliners ahead of the worldwide grounding of Boeing\'s next generation aircraft earlier this month. A spokeswoman for All Nippon Airways said 10 batteries on its fleet had been switched, while a representative of rival Japan Airlines (JAL) told AFP \"quite a few\" had needed changing. The lithium-ion batteries, made by Japanese manufacturer GS Yuasa, have been at the centre of a probe into the Dreamliner\'s airworthiness since a fire on a JAL plane in Boston and an emergency landing on an ANA flight in Japan. ANA, a key customer for Boeing\'s lightweight plane, had to replace batteries 10 times ahead of the January 16 emergency landing forced by smoke apparently linked to the powerpack, a company spokeswoman said. \"Batteries in general have to be replaced as frequently as need arises,\" a spokeswoman told AFP, without providing further details. It was not immediately clear if all 10 replacements had been carried out on different planes, or if the same aircraft had seen multiple changes. A JAL spokeswoman said it had \"quite a few cases\" where Boeing 787 batteries had to be replaced before the aircraft\'s worldwide fleet was grounded. ANA and JAL are important Dreamliner customers who have so far ordered a combined 111 aircraft.