Japan's All Nippon Airways says it replaced lithium-ion batteries on its 787 Dreamliners 10 times before a battery overheating incident led to the worldwide grounding of the jets.
ANA spokeswoman Megumi Tezuka said 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. Boeing was informed.
She said the batteries were replaced because they failed to charge properly or showed other problems.
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.