The US National Transportation Safety Board said Thursday that new tests should be conducted on batteries in Boeing's 787 Dreamliner, after causing two incidents last year.
In January 2013, regulators grounded the plane for three months following two battery overheating incidents that caused a fire on a 787 parked at Boston's Logan airport and smoke that forced an aircraft into an emergency landing in Japan.
The NTSB said on its website that a process used in 2006 to assess the lithium-ion batteries was "inadequate" and called on the US Federal Aviation Administration to develop more comprehensive assessments.
The agency made five recommendations, calling in particular for the evaluation of safety performance in the event of "an internal short circuit failure."
It also called for "a panel of independent expert consultants" to be involved early in the technology approval process.
Boeing said that tests conducted on the batteries after the 2013 incidents "are fully consistent with the recommendations made by the NTSB today."
"We therefore remain confident in the safety and integrity of the comprehensive battery solution which was developed by Boeing, and approved by the FAA, last year" when the airplane was allowed to fly again, the company said in a statement.
Because "airplane certification standards should and do evolve as the state of knowledge advances," Boeing said it would review the recommendations and supports "efforts to ensure that certification standards for lithium-ion batteries reflect and incorporate such advances."
Boeing's "green" passenger jet, the 787 Dreamliner, boasts of fuel-efficient design features and carries 210 to 330 passengers.