U.S. aviation authorities may soon lift the order grounding Boeing Co.’s 787 Dreamliner, aviation sources said Thursday, paving the way for airlines around the world to resume flights using the advanced jet.

Although the root cause of a series of smoky battery-related incidents involving the jet has yet to be identified, the U.S. Federal Aviation Administration has apparently judged that Boeing’s remedy for the troubled lithium-ion batteries eliminated the risk of fire, the sources said.

In the meantime, carriers including All Nippon Airways Co. and Japan Airlines Co. — the two biggest purchasers of the 787 — are not expected to resume flights involving the aircraft before June because the recommended modifications will take time to complete and pilots will need more training.

In March, Boeing proposed a set of solutions for the battery, such as design improvements and the addition of an enclosure to safely release heat and pressure generated by an adverse event.

The final test flight for demonstrating the new battery system took place earlier this month. U.S. and Japanese aviation authorities are scrutinizing the results, but no problems have been reported so far, the sources said.

A total of 50 Dreamliners were taken out of service worldwide after one operated by ANA made an emergency landing on Jan. 16 due to smoke in the cockpit. Its lithium-ion battery was later found to be severely damaged and charred.