Boeing today completed the final certification test for the modified 787 battery system during a demonstration flight for the FAA, using LN86, a production aircraft destined for LOT Polish Airlines.

The aircraft builder reveals that it also completed the crucial ground test of a deliberately failed battery on ZA005 earlier this week. Assuming Boeing gets good results from today’s flight test, which was to demonstrate that the new system performs as intended during normal and non-normal flight conditions, all data will be submitted to the FAA and Japanese Civil Aviation Bureau (JCAB) for approval.

Today’s flight of LN86, also known as ZA272, included FAA observers and began from Paine Field, Everett, Wash., at 10:39 am. For the test flight, the aircraft operated over the Washington and Oregon coasts and climbed to a maximum altitude of 43,000 ft. before returning to Everett.

Following regulatory approval of the updated battery installation, likely within the next two weeks, Boeing will issue a service bulletin to 787 operators detailing the modification package. Following approval of the service bulletin, which indicates that the modification complies with the terms stipulated by regulatory agencies for a return to flight, the FAA and JCAB will revise their respective airworthiness directives (AD). The FAA AD and the associated JCAB Technical Circular Directive prompted the grounding of the fleet in mid-January, following two battery failures on All Nippon Airways- and Japan Airlines-operated 787s earlier that month.

Boeing, working with airline teams in Japan, Qatar, Chile and the U.S., will then install the modified battery system in the aircraft. First to receive the installation will be an ANA aircraft in Japan, where a team of Boeing engineers has already begun preparatory work in anticipation of FAA/JCAB approval. Each modification is expected to take about five days to perform and, pending completion of the modification and pilot refresher training, airlines are now anticipating a return to 787 services in June.