A Boeing 787 Dreamliner (David McNew/Getty Images)
TOKYO (AP) - Japan's All Nippon Airways replaced lithium-ion batteries on its 787 Dreamliners 10 times before the jets were grounded worldwide due to battery problems, The New York Times reported late Tuesday.
ANA spokeswoman Megumi Tezuka told the Associated Press Wednesday the airline was not required to report the battery swapping cases to Japan's Transport Ministry because they did not raise safety concerns and did not interfere with flights.
She said the batteries were replaced because they failed to charge properly or showed other problems.
Boeing, which manufactures the Dreamliners, was informed.
In Seattle, Boeing spokeswoman Kate Bergman told USA TODAY that the company was aware of ANA's report but had no comment.
All Nippon told the Times that in five of the 10 replacements, the main battery had showed an unexpectedly low charge.
All 50 of the Boeing 787s in use around the world were grounded after an ANA flight on Jan. 16 made an emergency landing in Japan when its main battery overheated. Earlier, a battery in a Japan Airlines 787 caught fire while parked at Boston's Logan International Airport.
In the United States, the National Transportation Safety Board and Federal Aviation Administration are conducting an investigation of the Boeing 787's battery problems. U.S. regulators said Wednesday they asked Boeing to provide a full operating history of lithium-ion batteries used in its grounded 787 Dreamliners.