(New throughout, adds details about company stakes, testing)
July 10 (Reuters) - General Electric Co said on Thursday it picked France's Safran SA, Japan's IHI Corp and Germany's MTU Aero Engines AG to work on the GE9X engine that will power Boeing Co's new 777X aircraft.
GE told Reuters the companies chosen would share about 25 percent of the GE9X program, with Safran holding the largest share. The companies already are partners on other GE engine programs, and will pay the development cost of their components.
GE said it will invest $300 million in the GE9X program this year, and key parts already are being tested, including composite fan blades at a Boeing wind tunnel in Seattle.
GE has orders for more than 600 GE9X engines, the sole engine choice on the 777X, Boeing's latest twin-aisle jetliner due to enter service in 2020.
On Wednesday, Dubai-based Emirates Airlines finalized plans to buy 150 of the aircraft, worth $56 billion at list prices, part of $100 billion in commitments announced at the program launch last November.
Safran's said it will have a stake in the engine program of just over 11 percent.
Its Snecma and Techspace Aero units will make the composite forward fan case, the low-pressure compressor and other parts, Safran said.
Snecma will make composite fan blades through its 50-50 CFAN joint venture with GE. Safran and GE already collaborate in the CFM International joint venture that is developing engines for the forthcoming Boeing 737 MAX and Airbus Group NV A320neo jets, among other jets.
IHI Corp will have at least a 10 percent share in the in the GE9X program, and will design and manufacture components for the low-pressure turbine and the fan mid-shaft, GE said.
MTU will have a 4 percent stake, and will make the center frame of the turbine, GE said.
GE said it has been testing key technologies for the GE9X over the last few years. It completed tests on a high-pressure compressor in Italy earlier this year, and plans to test ceramic matrix composite components later this year.
(Reporting by Alwyn Scott in New York; Editing by Franklin Paul, Jeffrey Benkoe and David Gregorio)