Japanese airlines on Wednesday hoped for a rapid resumption of Dreamliner operations after US authorities approved test flights using a prototype battery fix following a global safety scare.

The worldwide grounding of Dreamliners has thrown schedules into disarray, especially in Japan where All Nippon Airways (ANA), the biggest operator of the plane, has been forced to cancel more than 3,600 flights to the end of May.

"ANA, as the launch customer of the 787, hopes its flights will be resumed as early as possible on condition that safety is guaranteed," said a spokesman for the airline, which hailed the Federal Aviation Administration (FAA) approval.

"We think the approval... is major progress towards resuming operations of the 787," he said.

A spokesman at Japan Airlines (JAL) said the company believed the issue had "entered a new stage", adding the firm would continue to work in cooperation with parties concerned.

Battery maker GS Yuasa declined to comment when contacted by AFP.

Japanese investigators who have been dispatched to Seattle will also take part in the FAA's safety reviewing process, a transport ministry official said Wednesday.

"The FAA takes the primary responsibility in the safety screening," said the ministry official, adding that it was the first time that representatives from Japan -- neither the home of the manufacturer nor the regulator -- would take part in such safety reviews.

Japanese airline shares climbed Wednesday on the Tokyo Stock Exchange, bucking a fall in the headline index.

ANA shares were up 1.48 percent to 205 yen by the close and JAL was up 1.70 percent to 4,470 yen.

US regulators Tuesday approved Boeing's plan for the 787 batteries and said the company could carry out test flights with the fix.

"The Federal Aviation Administration... approved the Boeing Commercial Airplane Company's certification plan for the redesigned 787 battery system... and the company's plan to demonstrate that the system will meet FAA requirements," the agency said in a statement.

The FAA said it had given the go-ahead after "thoroughly reviewing" Boeing's February 22 plan to address risks after lithium-ion batteries malfunctioned on two 787 Dreamliner aircraft in mid-January.

A short circuit started a fire on a parked 787 at Boston's Logan Airport and smoke from a battery forced an emergency landing in Japan.

The incidents led to the grounding of all 50 787s in service worldwide on January 16.

The US aircraft giant, which has bet heavily on its lightweight plane at a time when airlines are eager to slash fuel costs, desperately wants to get it back in the air.

Japan's Mainichi Shimbun newspaper quoted a transport ministry official as saying that Dreamliner operations "may resume as early as late April if (the safety review) proceeds smoothly."

But another ministry official denied the report.

"We are not in a position to say anything" on the timing, he said. "The work to prove the safety (of the aircraft) has not even started."

The global grounding of the Dreamliner has played havoc, especially in Japan.

JAL, which had been expecting delivery of three new Dreamliners by the end of March, has said it was slashing its schedules over the next three months.

But in a vote of confidence for the planemaker, Shinichiro Ito, president of ANA -- the biggest customer of the plane so far with 17 in service -- has said the company would stick with the 787.