RENEE MONTAGNE, HOST:
Investigators in London are continuing to probe the cause of last Friday's fire onboard a parked Boeing 787 - the plane known as the Dreamliner. They're examining what role the emergency locator transmitter might have played.
That device is made by Honeywell - and as NPR's Wendy Kaufman reports, the company has sent technical experts to assist in the investigation.
WENDY KAUFMAN, BYLINE: The emergency locator transmitter, or ELT, sends out a digitally encoded signal after a crash, and says aviation analyst Scott Hamilton...
SCOTT HAMILTON: Search teams would rely on signals emitted from the ELTs to locate the airplane.
KAUFMAN: These emergency beacons are on every commercial jet. In a statement, Honeywell says its ELT was certified by the FAA in 2008 and there haven't any reported incidents with the device. It's powered by a very small non-rechargeable lithium manganese battery. It's normally quiet and not doing anything while a plane is parked.
This investigation comes roughly three months after the 787s were returned to service after being grounded because of serious problems with a different kind of battery. Investigators have said those lithium ion batteries are not implicated in this incident.
Aviation expert Han Weber says, while we still don't know how this fire started, humans have been to blame for fires on other parked jets.
HAN WEBER: Somebody smoking a cigarette illegally on the aircraft and not extinguishing the cigarette properly or somebody leaving something on the hot plate or somebody doing a repair job and causing a fire to smolder without noticing it.
KAUFMAN: Investigators are expected to have a least some answers in a matter of days.
Wendy Kaufman, NPR News. Transcript provided by NPR, Copyright NPR.