Ethiopian Airlines is set to become the world's first carrier to resume flying Boeing Co's 787 Dreamliner passenger jets, with a commercial flight on Saturday to neighbouring Kenya, two airline sources said.

Boeing's Dreamliners have been grounded since regulators ordered all 50 planes out of the skies in mid-January after batteries on two of them overheated. U.S. regulators approved a new battery design on Friday, clearing the way for installation.

"Ethiopian Airlines will be the first airline company to resume 787 Dreamliner flights in the world. Saturday's the date," a senior Ethiopian Airlines source told Reuters. "We're flying to Nairobi, Kenya on the normal flight schedule."

Another source, who also declined to be named, confirmed the plan to resume flights on Saturday by the airline, the first African carrier to purchase Dreamliner planes. It ordered 10, has received four, and started flying them in August.

The grounding has cost Boeing an estimated $600 million, halted deliveries and forced some airlines to lease alternative aircraft. Several airlines have said they will seek compensation from Boeing, potentially adding to the plane maker's losses.

The U.S. Federal Aviation Administration (FAA), which grounded the planes, is expected to issue an Airworthiness Directive on Thursday. This applies to U.S. airlines, but other nations are expected to follow suit immediately.

Randy Tinseth, Boeing's vice president for marketing, said in the Ethiopian capital that the planes for all airlines would be modified and would work with their own regulatory authorities to determine when flights would resume.

"Each airline will be a little bit different," he told reporters.

Ethiopian Airlines previously said its fleet did not suffer any of the technical glitches experienced by other Dreamliner jets, though it withdrew the planes from service to undergo special inspection requirements mandated by the FAA.

(Additional reporting by Alwyn Scott in New York; Writing by Drazen Jorgic; Editing by Edmund Blair and Keiron Henderson)