Boeing has started 787 battery system modifications on 10 in-service fleet aircraft and believes modifications will be completed on nearly all 50 in-service fleet aircraft by mid-May.

A US National Transportation Safety Board (NTSB) hearing on the Jan. 7 Japan Airlines Boeing 787 fire shed little light on the incident’s root cause.

Extensive testing on lithium ion batteries during the 787 certification process led Boeing to believe that “significant overcharging” was the only occurrence that would cause the batteries to vent fire, according to a senior Boeing executive.

Air India is preparing to have its six Boeing 787s back into service by the middle of May, according to airline officials in Mumbai.

Boeing is deploying 10 teams comprised of 300 specialists around the world to perform FAA-approved modifications on the 50 787s that were in service when the Dreamliner fleet was grounded Jan. 16.

FAA has approved Boeing’s design modifications for the 787 battery system, paving the way for the lifting of the grounding of the worldwide Dreamliner fleet imposed Jan. 16.

Boeing’s more than three-month 787 crisis appears to be over following FAA’s approval of the manufacturer’s fix for the aircraft’s battery system.

Boeing has been given permission by FAA to resume pre-delivery 787 production flights and operated a production flight Thursday with an All Nippon Airways-bound 787.