Anticipating a new generation of single-aisle airliners from Airbus and Boeing Co.,  jet-engine maker CFM International plans in 2019 to shift production of its current CFM56 model to its improved Leap engines, the joint venture's director said Saturday.

The CFM56 is the current version of one of the most successful jet engines ever developed. CFM, a joint venture of General Electric Co. and Safran SA of France, will replace it with the more efficient Leap model.

Despite the planned wind-down, CFM plans to announce four to five CFM56 orders this week at the Farnborough International Air Show.

CFM has a growing backlog of orders for Leap engines to power more than 2,700 aircraft for Boeing, Airbus and Comac of China. Cédric Goubet, CFM program director for the CFM56 and Leap engines, said the venture will largely phase out regular CFM56 engine production near the end of the decade, as Boeing and Airbus shift to their newer models.

Neither Boeing nor Airbus, a unit of European Aeronautic Space & Defence Co., has said when it will curtail production of its current generation narrowbodies and switch to producing only their new models, 737 Max and A320neo. The Leap is the sole engine available for the 737 Max and one of two choices on the A320 neo, or new engine option. The Chinese Comac C919, now in development, also will be powered by a CFM Leap engine.

A Boeing spokesman said the company hasn't decided when it will stop producing the current version of its 737 and the decision will be driven by demand for the plane. Airbus says the decision will be driven by customers and has no set plans to end current generation A320 production; company leaders have said Airbus could transition fully to A320neo production by 2018.

The CFM56 is the engine on Boeing's current 737NG models and is one engine available on the Airbus A320. The other is the International Aero Engines V2500, produced by Pratt & Whitney, a unit of United Technologies Corp.

CFM expects to deliver 1,400 engines in 2012, with that number expected to climb above 1,500 by 2014 and 1,700 in 2020, Mr. Goubet said.

The first model of the Leap engines for Airbus's planned A320neo model and for the C919 will begin ground testing in the third quarter of 2013. The two versions of the engines are almost identical, CFM says.

Engines for both planes are scheduled to enter service in the second quarter of 2016, though the C919's development schedule has remained in question as the state-owned company has struggled with development of its ARJ21 regional jet. Boeing is developing a new version of its 737, dubbed the Max, which will use the Leap engine. It expects to deliver the first 737 Max at the end of 2017.

CFM Executive Vice President Chaker Charour said the venture will maintain the ability to produce CFM56 engines, but doesn't expect to supply more than 100 to 120 engines per year by 2019, or enough for about 50 to 60 aircraft, as well as spare parts.

John-Paul Ebanga, CEO of the joint venture has said CFM has this year booked orders to supply engines for 480 airplanes with 100 seats or more, giving CFM a 62% share of the overall market this year. The company is expected to announce more orders during the air show near London, which runs from July 9 to 15.