The fault, found in the fire-suppression system of a 787 due to depart Tokyo's Haneda airport today, would cause the wrong extinguisher to be activated in the event of a blaze in one of the plane's two engines, spokeswoman Megumi Tezuka said.
Boeing's flagship jet is already under scrutiny following a fire in London last month that initial findings suggested may have been sparked by wires for an emergency beacon. The 787 had returned to service with ANA and Japan Airlines on June 1 after a global grounding in the wake of fires involving jets flown by the pair, later traced to the failure of lithium-ion batteries.
"We will thoroughly examine this issue and take the appropriate steps," Boeing spokesman Rob Henderson said from Tokyo following the latest incident. "The safety of those flying on Boeing airplanes is our top priority."
Boeing fell as much as 1 percent and was trading 0.8 percent lower at $105.4 as of 9:47 a.m. in New York. The stock has advanced 40 percent this year.
ANA's Tezuka said parts were replaced in two of the jets in which the Tokyo-based carrier found the defect, adding it must have occurred during the manufacturing process. The third aircraft will also be fixed by the end of the day, she said.
Japan Air today ordered a 787 bound for Helsinki to return to Narita airport in Tokyo as a precautionary measure after being informed of the new wiring issue by the national Transport Ministry, company spokesman Seiji Takaramoto said.
The carrier subsequently inspected all 10 of its 787s and found no problems, he said. Among other Dreamliner operators, LOT Polish Airlines SA said its planes are flying as scheduled, while Qatar Airways Ltd. said it has had no problems and Norwegian Air Shuttle ASA said it was unaware of the issue.
"These things happen with a new aircraft," said Robert Stallard, an analyst at RBC Capital in London with an "outperform" rating on Chicago-based Boeing. "When the airlines ground the plane or regulators start becoming involved, then it becomes something to watch out for."
U.S. regulators ordered Dreamliner operators to check emergency radio transmitters for wire damage after a beacon was linked to the July 12 fire in London. The Federal Aviation Administration is working with Boeing to develop instructions for the inspections, the agency said at the time.
Boeing had delivered 73 Dreamliners to 13 customers through August 7, the company said on its website, with more than 29,000 flights flown. Japan is the biggest customer of the jet.
Dreamliner operators resumed services after a three-month grounding over the battery fires when authorities approved a redesign including more protection around individual cells to contain overheating. Ethiopian Airlines Enterprise was first to restart flights in April, with the Japanese carriers opting for a four-month halt as they took out ads saying the 787 was safe.