Wiring faults discovered in troubled Boeing 787s

TOKYO — ANA Holdings, the world’s largest operator of Boeing 787 aircraft, said it found wiring defects in three of its Dreamliners, a discovery that prompted rival Japan Airlines to order a flight to return home.

ANA found improper wiring for the fire-suppression system on a Dreamliner before it was to depart from Tokyo’s Haneda airport Wednesday, spokeswoman Megumi Tezuka said by phone.

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The faulty wiring activates the wrong fire extinguisher in the event of a fire in one of the two engines, she said, adding the defect occurred during manufacturing.

The Tokyo airline replaced parts in two of the aircraft in which it found the defect, she said. The carrier operates a fleet of 20 787s.

‘‘We will thoroughly examine this issue and take the appropriate steps,’’ Rob Henderson, a spokesman for Boeing, said in Tokyo.

Bloomberg News