Japan’s All Nippon Airways (ANA) said it put its Dreamliner fleet back into service on Sunday following a suspension of about four months due to battery problems. ANA, the single biggest operator of Boeing’s flagship 787, said one of the high-tech planes departed “safely” on Sunday afternoon from Sapporo in Hokkaido to Haneda in Tokyo. It was ANA’s first commercial flight of Dreamliners since the planes were grounded worldwide after two separate incidents on Japanese-owned planes involving overheating of the lithium-ion battery packs in January. Last week ANA announced plans to resume the flights earlier than its originally planned date of June 1 as the airline completed safety tests. After months of investigations, US authorities in April formally approved Boeing’s battery fix and Japanese regulators followed suit. In mid-May ANA said a modified Dreamliner had experienced a fault in an electrical panel earlier in the month. But it insisted the glitch was too “minor” to affect the restart of services by the fuel-saving lightweight planes. ANA operates around a third of the 50 787s that Boeing has delivered. Last Monday United Airlines resumed a Boeing 787 Dreamliner flight from the airline’s hub in Houston, Texas, to Chicago.