Story highlights The Boeing 787 Dreamliner was back int he skies Saturday

The fleet had been grounded for more than three months because of safety concerns

The FAA approved a fix and Boeing began installing redesigned battery systems

The Ethiopian Airlines flight carried passengers from Addis Ababa to Nairobi

More than three months after safety issues grounded the Boeing 787 Dreamliner, Ethiopian Airlines became the first to resume service with a commercial flight Saturday.

Nearly 50 Dreamliners around the world had been out of commission after two incidents on jets operated by Japanese airlines called the battery systems into question.

Boeing last week began installing a redesigned battery system in the aircraft.

The Ethiopian Airlines Dreamliner flight carried passengers from Addis Ababa to Nairobi, Kenya, the company said.

The move follows the U.S. Federal Aviation Administration posting a directive outlining the modifications necessary for the Dreamliner to fly again.

Japan this week authorized its passenger airlines to resume Dreamliner flights, but it wasn't clear when they they would reinstate the aircraft.

The Dreamliner's use of lightweight composite materials to greatly improve fuel economy has made it a big seller in Asia and the Middle East, where long-haul flights account for much of an airline's business.

United Airlines, which has six Boeing 787 aircraft, is the only U.S. airline to take delivery of the Dreamliner so far. It will cost the airline about $2.8 million to implement the fix, according to the FAA's Federal Register filing.

The company plans to begin domestic flights using the 787 in May and possibly launch the Denver-Narita, Japan, route on June 10.