NEW YORK — Federal regulators said Wednesday that they had approved one flight of a Boeing 787, with a flight crew but no passengers, as the company’s engineers study possible changes to the plane’s electrical systems that could reduce the risk of another battery fire.
The flight would be the first for a 787 since aviation authorities grounded the innovative aircraft last month after two incidents with its lithium-ion batteries. The Federal Aviation Administration said it would let Boeing return one 787 from a painting plant in Fort Worth, Texas, to its plant near Seattle. It has not yet approved flights to conduct tests on the batteries.
The flight, scheduled for Thursday, will come as the National Transportation Safety Board is expected to raise questions about how the FAA certified the 787’s battery before it began flying passengers in 2011. The safety board, which has been performing tests of its own as part of its investigation into the battery problems, is seeking to find out why weaknesses with the batteries were not picked up in Boeing’s original testing program.
The safety board is looking at whether the FAA fully understood any potential issues with the volatile new batteries before it approved their use under special conditions.
Deborah Hersman, the safety board’s chairwoman, told reporters Wednesday that it would probably take investigators several more weeks to determine what had happened with the Boeing batteries.
Boeing engineers are working on a range of possible technical overhauls. These include making the battery cells more resistant to shocks to keep excess heat from spreading from one cell to another, causing the kind of thermal runaway that occurred in the two recent events. Boeing officials have said that they are also working on building more solid containment cases and better venting mechanisms in the event of overheating.
The 787 is the first commercial airplane to use large lithium-ion batteries for major flight functions. All 50 of Boeing’s 787s that were delivered to airlines have been grounded since mid-January.
“I would not want to categorically say that these batteries are not safe,’’ Hersman said during a briefing with reporters Wednesday. ‘‘Any new technology, any new design, there are going to be some inherent risks. The important thing is to mitigate them.’’
Boeing officials said that they were exploring numerous ways to strengthen the batteries and that it was premature to think any of those would be approved by regulators without more information.
The FAA’s decision to certify the batteries has come under scrutiny in recent weeks. While the federal regulator is stretched thin with too few inspectors, and typically relies on testing data from Boeing, lithium batteries are an area where the agency has some expertise. It has had to deal for years with fires involving lithium-ion batteries shipped as cargo or carried by passengers in their computers or cellphones.
Hersman will provide an update Thursday on the investigation’s process. But while she said the safety board was in a position to rule out some problems, it was unlikely to be able to say what happened for some time.
She said that she would not rule out the use of lithium batteries ‘‘categorically,’’ but insisted that the safeguards Boeing had put in place failed when a Japan Airlines plane experienced a fire while parked at Logan International Airport in Boston.
“Obviously what we saw in the 787 battery fire in Boston shows us there were some risks that were not mitigated, that were not addressed,’’ she said. She added that the fire was ‘‘not what we would have expected to see in a brand-new battery in a brand-new airplane.’’
The fleet’s grounding is not affected by the one-time FAA permit and no one except crew members will be allowed on board the plane from Fort Worth.
The FAA said that before takeoff, the Boeing crew should perform a number of inspections to verify that the batteries and cables showed no signs of damage.
While airborne, the crew must also ‘‘continuously monitor the flight computer for battery-related messages, and land immediately if one occurs,’’ the FAA said.