Top All Nippon Airways (ANA) and Boeing executives flew aboard the airline’s first 787 proving flight Sunday.

Ethiopian Airlines resumed Boeing 787 Dreamliner service Saturday with a flight from Addis Ababa to Nairobi, making it the first carrier to relaunch 787 flights since the aircraft was grounded in January.

All Nippon Airways (ANA), the Boeing 787 launch customer and largest Dreamliner operator with 17 in its fleet, will conduct a 787 proving flight Sunday, an initial step toward resumption of commercial flights with its 787s.

LOT Polish Airlines plans to resume Boeing 787 operations June 5, initially deploying the type on its Warsaw-Chicago service.

Japan’s Ministry of Land, Infrastructure, Transport and Tourism has approved Boeing’s fix for the 787’s battery system.

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.