Boeing has asked US government regulators to allow it to conduct test flights of its grounded 787 Dreamliner.
The news is being treated as positive as it suggests engineers have a good idea of what areas to stress-test.
Boeing and the Federal Aviation Administration both decline to provide more information.
The FAA grounded the world fleet of 50 787 Dreamliners on January 16 and regulators, including the National Transportation Safety Board, began investigating the lithium-ion batteries on the planes.
In Japan, where most of the Dreamliners in service are based, authorities are also investigating the planes.
The Japan Transportation Safety Board says CAT scans and other analysis have found damage to all eight cells in the lithium-ion battery that overheated on an ANA 787 that made an emergency landing after its pilots smelled something burning and received a cockpit warning of battery problems.
They also found signs of short-circuiting and “thermal runaway,” a chemical reaction in which rising temperature causes progressively hotter temperatures.
US investigators have found similar evidence in the battery that caught fire on a Japan Airlines 787 while parked in Boston.
The 787 is the first Boeing plane to use rechargeable lithium-ion batteries for its main electrical system.
“Boeing has teams of hundreds of engineering and technical experts who are working around the clock with the sole focus of resolving the issue and returning the 787 fleet to flight status,” Boeing spokesman Marc Birtel says.
“Everyone is working to get to the answer as quickly as possible and good progress is being made.”