Investigators are looking into whether a fire on a Boeing Dreamliner in London last week was caused by the battery of an emergency locator transmitter built by Honeywell International, according to a source familiar with the probe.
Passengers and investors appeared to take the news in stride, as airlines continued to fly the Boeing 787 and shares in the company regained most of what they lost on Friday, closing up 3.7 percent at $105.66 on Monday. (For Boeing's latest stock price, click here.)
Honeywell said it had joined the investigation into Friday's fire aboard the parked 787 at Heathrow airport but declined to discuss details beyond saying it had no previous experience of difficulties with this type of transmitter.
Boeing declined to comment on the transmitter.
In 2009, the Federal Aviation Administration told airlines that a Honeywell transmitter had failed in tests and advised them to replace it. Other global regulators published similar advisories.
There was no indication of fire risk from the unit.
Honeywell said it was checking whether the transmitter on the Ethiopian Airlines jet was the same model as one cited by regulators in 2009.
The 787 transmitter is in the aft fuselage section and a fire from it was "theoretically possible," said John Hansman, an aeronautics professor at MIT who has been an adviser to the FAA.
But Hansman said it seemed unlikely that the unit had malfunctioned. He said it was at least as likely that a passenger sneaked a cigarette in the lavatory and it smoldered for hours while the plane was parked at a remote stand at Heathrow before bursting into flames.
Britain's Air Accident Investigations Branch (AAIB), which is leading the probe into the fire, said on Saturday it found no evidence the fire was caused by the lithium-ion batteries that were implicated in the 787's grounding earlier this year.
(Read more: 787 fire: Investigators focus on key component)
The overheating in January of two battery packs that provide backup power to the plane caused regulators to ground the plane for three months and caused fleet-wide retrofits and delivery delays.