The British Air Accidents Investigation Branch said in a statement that the fire resulted in smoke throughout the plane and extensive heat damage in the upper part of the rear fuselage. But while the investigators said they had not found the cause of the problems, the damage was not near either of the plane’s lithium-ion batteries. “At this stage,” the statement said, “there is no evidence of a direct causal relationship” between the batteries and the fire.

That initial finding was a big relief to Boeing, its investors and the 13 airlines that have bought the planes, which were grounded for four months worldwide this year after two episodes involving fire or smoke from the batteries. But the eventual findings about the cause of the latest fire, which occurred on an unoccupied Ethiopian Airlines 787 parked at Heathrow Airport on Friday, could still be a setback for Boeing if the investigators find problems with another crucial system on the plane.

The investigation branch said its initial inquiry would most likely take several days, and it did not offer any other comment on possible causes. Other safety experts said the possibilities could include heated elements left in a galley just below where the fire burned through the jet’s carbon-composite skin, a poorly installed part or a short in the plane’s electrical system.

The innovative planes were grounded in mid-January after the incidents involving fire or smoke coming from the new and more volatile types of batteries. But the first 50 planes began flying again between late April to early June after regulators approved a series of fixes, including adding insulation between the battery cells and encasing the batteries inside a steel box.

Ethiopian Airlines said in a statement earlier on Saturday that it was continuing to fly its other 787s because the fire at Heathrow occurred after the jet had been on the ground for eight hours and “was not related to flight safety.” The airline did not comment on the possible cause of the fire.

The other airlines with the planes, including United Airlines and 11 other foreign carriers, have also continued to fly them while the fire at Heathrow is investigated.

The fire caused no injuries, but it disrupted travel, and investors reacted nervously, sending Boeing’s shares down 4.7 percent on Friday.

Smoke came from the plane, named the Queen of Sheba, eight hours after it had been parked in a remote space at Heathrow and about four and a half hours before it was scheduled to depart for Ethiopia. No passengers were on the plane, which was connected to an external ground power source, according to people briefed on the episode.

It was also not clear if any maintenance was under way or how long the fire had been burning, though it was intense enough to burn through the top of the fuselage near the tail. That area is in a complex section where large parts of the plane are joined together. The two lithium-ion batteries, which were used instead of conventional nickel-cadmium batteries to save weight and provide more energy, are under the cockpit and just behind the wings toward the bottom of the plane.

In addition to the British investigators leading the inquiry, a team from Boeing was on site along with representatives from the airline and from two American government agencies, the Federal Aviation Administration and the National Transportation Safety Board.

Boeing, the F.A.A. and the N.T.S.B. had no comment Saturday on the possible cause of the fire, deferring to the British investigators.

Other experts said that some of the plane’s wiring, and the oxygen systems for passengers, would have passed through the damaged area, which was above the rear galley. It was also possible the fire migrated from another part of the plane, they said.

The Financial Times quoted an Ethiopian manager in Britain as saying that maintenance workers had discovered a problem with the plane’s air-conditioning system during a routine inspection and had seen sparks but no flames. The report did not say when the inspection occurred, and aviation-safety officials in the United States were not sure what to make of it.

Thomson Airways, a charter airline, said on Saturday that it had replaced and tested several parts on a 787 that had cut short a flight on Friday. It said the plane would fly again on Sunday.

The 787 has had a history of other mishaps since entering service in November 2011. Several airlines, including United, Qatar Airways and All Nippon Airlines, have been forced to divert flights because of electrical problems or other reasons. Still, airlines have eagerly anticipated the plane, which has cut fuel costs by 20 percent.

Article source: http://www.nytimes.com/2013/07/14/business/fire-on-boeing-787-dreamliner-at-heathrow-in-london.html?partner=rss&emc=rss