European safety authorities have approved the design changes to the Boeing 787's battery system.
Clearance by the European Aviation Safety Agency means that Polish carrier LOT, and other European customers, will be able to operate the type once modified.
Boeing has detailed the locations of the 50 in-service 787s which will need the new battery, charger and containment system.
Ten teams of specialists are being sent to various locations to carry out the work.
EASA says it "certifies" that the changes proposed by Boeing meet its requirements. Its 787 directive on the matter will be updated to allow the jets under its remit to return to service as soon as the installations are complete.