A probe into a Japan Airlines Boeing 787 Dreamliner has been widened by US safety officials after ruling out overcharging as the cause of a battery fire.
The focus is now on the battery charger and the aircraft’s auxiliary power unit.
Boeing said on Friday it would put deliveries of the 787 on hold until the Federal Aviation Administration approved its plan to ensure the safety of the batteries.
Thomson Airways and British Airways are due to receive their first Dreamliners in May but it remains unclear whether that deadline will be met.
Regulators grounded all Dreamliners in operation last week after an All Nippon Airways flight had to make an emergency landing.
The aircraft was forced to land after a warning light came on in the cockpit, saying there was a problem with one of the 787’s batteries.
Japanese investigators looking into the cause of the lithium-ion battery malfunction on the ANA flight indicated that an overcharged battery may have been the cause.
The US National Transportation Safety Board said overcharging was not the case in the JAL incident in Boston.
“Examination of the flight recorder data from the JAL B787 airplane indicates that the APU (auxiliary power unit) battery did not exceed its designed voltage of 32 volts,” the NTSB said.
Boeing commercial aircraft marketing vice president Randy Tinseth said: “The company is working around the clock with its customers and the various regulatory and investigative authorities.
“We will make available the entire resources of The Boeing Company to assist. We are confident the 787 is safe and we stand behind its overall integrity.
“We will be taking every necessary step in the coming days to assure our customers and the traveling public of the 787’s safety and to return the airplanes to service.
“According to the FAA’s recent announcement, operations can resume once airlines have demonstrated the batteries are safe. Boeing is working with the FAA to define that process and timeline.”