( CNN ) -- A fire and `` technical issue '' aboard two Boeing 787 Dreamliners on Friday raised new safety concerns for the long troubled airliner . The fire ignited on an empty 787 operated by Ethiopian Airlines that was parked at London 's Heathrow airport . No one was hurt and the incident shut runways for about an hour before operations resumed , the airport said . Details were unclear about the fire 's cause or location aboard the plane , but the incident was enough to spur U.S. aviation experts to investigate . In a separate incident on Friday , Thomson Airways reported a `` technical issue '' aboard its Dreamliner flying from Manchester , England , to Florida . The aircraft returned to Manchester as a `` precautionary measure , '' Thomson said in a statement . Engineers were `` inspecting the aircraft , '' the statement said . Passengers were transferred to another plane . The airline offered no other details of the problem . Related : Dreamliner interactive layout . The Dreamliner , which has been flying since 2011 , has been closely watched since last January when all 50 of the world 's 787s were grounded due to overheating problems in its new light-weight lithium-ion battery system . The planes were allowed to return to service in April after Boeing engineered a solution that satisfied U.S. aviation authorities . Heathrow reopened Friday evening and Boeing officials were at the airport to analyze the problem , the company said . Ethiopian Airlines : Bringing the Dreamliner to Africa . It was not known if the battery system was associated with the latest incident , but a statement released by Ethiopian Airlines said the jet had been `` parked at the airport for more than eight hours '' before the fire . The Federal Aviation Administration is sending `` an official '' at the invitation of the British government , the agency told CNN in a statement . The FAA said earlier it was `` in contact '' with Boeing about the matter . The National Transportation Safety Board tweeted it also was sending an `` accredited representative '' to the airport to help the investigation . Friday 's fire triggered renewed doubt about the 787 among the aviation community , including aviation lawyer and former U.S. Department of Transportation Inspector General Mary Schiavo . `` If today 's Boeing 787 problems are battery related , '' she tweeted , `` the FAA may reconsider its decision to allow them to fly before NTSB identified '' what caused the battery troubles . Video of the aftermath showed foam surrounding the Ethiopian aircraft and what appeared to be burn marks on its fuselage . `` There 's still hope for Boeing , '' Schiavo tweeted later . `` The burn marks are not next to the batteries . '' Japanese Dreamliner held due to A/C power glitch . The news sent Boeing 's shares on Wall Street down more than 4 % . Boeing 's stake is huge . Hundreds of millions of dollars are riding on the success of the Dreamliner , which represents a new generation of lighter , more efficient money making airliners . Its development was marked by production delays and other problems . During their first few years in service , every airliner experiences `` teething pains '' as they shake out minor problems , experts say . But the FAA 's decision to ground the Dreamliner put it under a microscope . The lone U.S. 787 operator -- United Airlines -- owns a fleet of six . During a six-day period in June , United diverted three of them , each with a different mechanical problem . Indicators showed possible issues with oil levels , oil filters and the braking system . Related : Another 787 Dreamliner diverted for mechanical problem . Dreamliner 's lithium-ion batteries were blamed for two overheating instances this year in Boston and Japan . No one was hurt in either case , but the problems spurred the FAA to ground the planes . In March , the FAA approved a Boeing certification plan to fix the 787 battery system and prove the new design is safe . A team of experts from Boeing and from outside the company redesigned parts of the battery system in what they called a `` robust '' fix that included separating the battery cells , integrating a new charging system , and setting the batteries in a containment box that would vent outside the aircraft any smoke from overheating batteries . Related : Behind the scenes for Boeing 's 'robust ' battery fix . The Dreamliner boasts high fuel efficiency because of the lightweight carbon composite materials used in its wings and fuselage . Related : Can 'game-changer ' Dreamliner live up to its name ? In an apparent show of confidence in the new aircraft , United announced last month that it was ordering 20 additional 787s , specifically the 787-10 model , a longer version of the plane . CNN 's Aaron Cooper , Richard Quest , Scott Hamilton , Jason Hanna and Richard Greene contributed to this report .
NEW : Ex - DOT official confirms that burn marks are not next to the batteries . It says it 's sending ` ` an official '' to Heathrow after Dreamliner fire . ` ` Techncal issue '' aboard a second Dreamliner crash , forces it to return to service . A fire breaks out on an empty United Airlines Boeing 737 at Heathrow airport .