LONDON -- A fire aboard an empty 787 at London's Heathrow Airport spooked Boeing investors Friday, as they feared the re-emergence of battery problems that grounded the plane for months earlier this year.
Boeing shares lost $5.01, or 4.7 percent, to $101.87. At its peak, the selling knocked off $7.89 a share, or $6 billion of market value. The stock recovered slightly as speculation about the cause of the fire shifted away from the batteries.
The cause of the fire on the Ethiopian Airlines plane -- which broke out more than 8 hours after it had landed in London -- remained under investigation. The fire's location led some experts to surmise that it wasn't the planes lithium-ion batteries.
Meanwhile, an unspecified mechanical issue caused another 787 flown by Thomson Airways to return to Manchester Airport, adding to concerns about the plane.
Runways at Heathrow were shut down for nearly an hour as emergency crews put out the fire. No passengers were on the plane.
The 787, which Boeing dubs the Dreamliner, was grounded in January following two incidents with its lithium-ion batteries. One 787 caught fire shortly after it landed Jan. 7 at Boston's Logan International Airport.
The FAA eventually approved a plan by Boeing to better insulate the battery's eight cells and the addition of a new containment and venting system. Once the changes were made, planes started to fly again.
Boeing marketed the plane to airlines as a revolutionary jet that -- thanks to its lightweight design -- burns 20 percent less fuel to comparable aircraft. Boeing, based in Chicago, has delivered 66 of the planes to customers, with another 864 on order.
Boeing's stock partially rebounded after photos circulated showing the plane section damaged by the fire, an area far from the battery compartment. The photos show the rear roof burned, near the jet's vertical stabilizer, often called the tail. The batteries are in two separate compartments under the plane's floor -- one near the wings, the other under the cockpit.
"Evidence thus far suggests that the battery was not the cause of the fire at Heathrow," Jason Gursky, an aerospace analyst with Citi told investors. "The images out of London are not consistent with the fire at Boston Logan, which prompted the grounding earlier this year." He added that "aircraft are complex animals such that a fire could come from many places." This incident could highlight a new problem with the 787, he said, causing further problems for Boeing.