Boeing has published the results of an investigation into the fire on a test flight earlier this month, which suggests airlines may not receive their new planes as scheduled.
The incident onboard test plane ZA002 forced the aircraft manufacturer to cancel all test flights until the cause had been found.
The new aircraft was due for its first delivery next year, to launch airline ANA, but many fear this may have to be pushed back.
In a statement, Boeing said a “revised” 787 program schedule will be finalised in the next few weeks.
The superjumbo is already more than three years behind its original schedule.
Scott Fancher, vice president and general manager of the 787 program, said: "We have successfully simulated key aspects of the onboard event in our laboratory.”
He said Boeing is “moving forward” with design fixes, and developing a plan to “enable a return to 787 flight test activities”, but did not say when this might be.
Engineers at Boeing found the fire began as either a short circuit or an electrical arc in the power distribution channel, due to “foreign debris”.
Boeing is now developing “minor design changes” to power distribution panels, as well as updates to the software that manages and protects power distribution.