Two weeks after completing the final certification test of the modified 787 battery system, Boeing appears to be on the verge of receiving FAA approval for the fix, clearing the way for fleet-wide installations to begin.

The FAA signaled tacit approval for the modification package on April 18 when it granted Boeing permission to resume routine production ‘B-1’ flight testing of an aircraft destined for All Nippon Airways (ANA). The move comes just over three months after the 787 was grounded following battery failures on a Japan Airlines aircraft in Boston on Jan. 7, and on an ANA flight which diverted to Takamatsu during a flight from Tokyo’s Haneda airport to Yamaguchi in western Japan on Jan. 15.

Boeing has pre-deployed teams of engineers to modify the first of 50 787s that had already been delivered when the grounding began. In addition, ground crews in Everett, Wash. and Charleston, S.C. have begun working through a further batch of up to 34 aircraft that were either awaiting delivery when the crisis began, or which have been assembled over the past four months. One of these is the latest for ANA, line number 83, which conducted the B-1 flight on April 18 complete with the revised battery system in place.

Assuming formal regulatory approval of the modified battery installation is forthcoming, Boeing will issue a service bulletin detailing the modification package. Following approval of the service bulletin the FAA and Japanese Civil Aviation Bureau (JCAB) will each revise their respective airworthiness directives (AD). The FAA’s directive, AD 2013-02-51, was issued just before an associated JCAB Technical Circular Directive which prompted the grounding of the fleet.

Boeing, working with airline teams in Ethiopia, Japan, Qatar, Chile and the U.S, will then install the modified battery system in the aircraft. Each modification is expected to take up to five days to perform, with the first 787s expected to return to service in May or June.