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CFM International LEAP

CFM International (GE Aviation + Safran Aircraft Engines) · Aircraft Engine · France / USA · Digital Age (2010–present)

CFM International LEAP — Aircraft Engine
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The CFM International LEAP (Leading Edge Aviation Propulsion) is a family of high-bypass turbofan engines that succeeded the CFM56 as the workhorse of the global narrow-body fleet. Built by the same 50/50 joint venture between GE Aerospace and Safran Aircraft Engines, LEAP entered service in 2016 and competes head-to-head with the Pratt & Whitney PW1000G geared turbofan on the Airbus A320neo, while holding sole-source status on the Boeing 737 MAX and the COMAC C919. By the end of 2025 more than 5,000 LEAPs had been delivered, and CFM's combined order backlog passed 10,000 units — the largest in commercial-aviation history.

LEAP raises bypass ratio from the CFM56's 5-6:1 to around 11:1, with a 78-inch fan on the LEAP-1A and 69-inch fan on the LEAP-1B. The fan blades are 3D-woven resin-transfer-moulded carbon-fibre composites, a CFM patent developed at Safran's Composites Aero Centre in Mexico, replacing the heavy titanium fans of the CFM56. The high-pressure turbine uses ceramic-matrix-composite (CMC) shrouds — the first commercial CMC application in turbine hot section — cutting cooling-air demand and raising thermal efficiency. A higher 22:1 overall pressure ratio in the core squeezes more work out of each kilogram of air. Combined, these changes deliver around 15% better fuel burn and 50% lower NOx emissions versus the CFM56-5B and -7B.

Three variants serve three airframes. The LEAP-1A (24,500-32,900 lbf) launched on the Airbus A320neo family in August 2016 with Pegasus Airlines, and now powers around 60% of A320neo deliveries — the rest go to the Pratt & Whitney GTF. The LEAP-1B (23,000-29,300 lbf, 69.4-inch fan) is the sole engine on the Boeing 737 MAX, entered service with Malindo Air in May 2017, and continues to ramp despite the 737 MAX grounding (2019-2020) and 2024 production-quality pauses. The LEAP-1C (27,980-30,000 lbf) entered service with the COMAC C919 in May 2023 on China Eastern Airlines and remains under U.S. export-licence review.

LEAP development cost roughly $4 billion, paralleling Pratt & Whitney's investment in the PW1000G. Entry-into-service issues included high-pressure-turbine durability problems on the early LEAP-1B fleet — exacerbated by hot-and-sandy operating environments — leading to lower-than-promised on-wing times and a 2018 redesign of HPT components. By 2022 the redesigned hardware had restored shop-visit intervals close to specification, and by 2025 the LEAP fleet had logged more than 50 million flight hours.

Forward-looking development includes the LEAP-1A26E1, a derated version for the COMAC C919 trans-Pacific configuration, and the RISE (Revolutionary Innovation for Sustainable Engines) open-fan demonstrator. RISE targets entry into service around 2035 with another 20% fuel-burn reduction over LEAP — and a fan diameter of around 140 inches, dispensing with a cowl entirely. RISE represents CFM's bet that the next generation of narrow-body propulsion will be ducted-fan no more.

For Kids — a shorter, friendlier version

The CFM International LEAP is a powerful jet engine. It helps push airplanes through the sky. You can find it on the Boeing 737 MAX, the Airbus A320neo, and the COMAC C919. These are some of the most popular passenger jets in the world today.

The LEAP first flew on real airlines in 2016. It was made by two companies working together: GE Aerospace and Safran Aircraft Engines. More than 5,000 LEAP engines have been built and delivered. Airlines have ordered over 10,000 more — the biggest order list in the history of air travel!

One cool thing about the LEAP is its giant fan at the front. The biggest version has a fan wider than a tall adult lying flat. The fan blades are made from a strong, light material called carbon fiber. This makes them lighter than the old heavy metal blades used before.

The LEAP also uses special heat-resistant parts inside called ceramic-matrix-composite shrouds. These parts can handle very high temperatures. This helps the engine burn fuel more cleanly and use less of it. That is great for the environment and saves airlines money.

The LEAP moves a huge amount of air around the engine, not just through it. This is called a high bypass ratio of about 11 to 1. Pushing more air this way makes the engine faster than older engines and much quieter too.

Fun Facts

  • The LEAP engine entered service in 2016 and quickly became one of the most popular jet engines ever made.
  • The biggest LEAP fan is 78 inches wide — wider than most adults are tall!
  • Over 5,000 LEAP engines have already been delivered to airlines around the world.
  • The fan blades are made from woven carbon fiber, making them lighter than the old titanium blades.
  • The LEAP was the first commercial engine to use ceramic-matrix-composite parts in its hottest section.
  • Airlines have ordered more than 10,000 LEAP engines — the largest order backlog in commercial aviation history.
  • The LEAP powers three different jet families: the Boeing 737 MAX, the Airbus A320neo, and the COMAC C919.
  • The LEAP's bypass ratio of 11 to 1 makes it much more fuel-efficient than the older engine it replaced.

Kids’ Questions

What does a jet engine actually do?

A jet engine sucks in air from the front and pushes it out the back very fast. This pushing force moves the airplane forward. The LEAP does this with a huge spinning fan and very hot burning gases inside.

Why are the LEAP fan blades made from carbon fiber instead of metal?

Carbon fiber is very strong but much lighter than metal like titanium. Lighter blades mean the engine does not have to work as hard. This saves fuel and helps the airplane fly more efficiently.

Which airplanes use the LEAP engine?

The LEAP engine is used on three popular jet families. These are the Boeing 737 MAX, the Airbus A320neo, and the COMAC C919. Millions of passengers fly on these jets every year.

What makes the LEAP better than older engines?

The LEAP moves more air, uses special heat-resistant parts, and has lighter fan blades. All of these things help it burn less fuel. It is also quieter than the older engines it replaced.

Variants

LEAP-1A
Airbus A320neo family variant (A319neo/A320neo/A321neo/A321XLR). 24,500-32,900 lbf, 78-inch fan, 11:1 bypass. Service entry August 2016 with Pegasus Airlines. Around 60% market share against the Pratt & Whitney GTF on A320neo orders.
LEAP-1B
Boeing 737 MAX sole-source engine. 23,000-29,300 lbf, 69.4-inch fan, smaller diameter chosen to maintain ground clearance under the 737's low wing. Service entry May 2017 with Malindo Air.
LEAP-1C
COMAC C919 variant with full integrated propulsion system (nacelle and thrust reverser supplied by Safran Nacelles). 27,980-30,000 lbf. Service entry May 2023 with China Eastern Airlines, subject to ongoing U.S. export licensing.
LEAP-1A26E1 (later)
Higher-thrust derate planned for the A321XLR and long-range C919 missions. Adds margin for high-altitude hot-day takeoffs without changing the core architecture.

Notable Operators

Boeing 737 MAX
Sole-source engine for the entire MAX family — MAX 7, MAX 8, MAX 9, MAX 10. Operators include Southwest Airlines (largest 737 MAX fleet globally), Ryanair, American, United, Alaska, Air Canada, and more than 80 other carriers. Delivery rates approached 40 per month at the 2024 peak.
Airbus A320neo family
Selected by around 60% of A320neo customers. IndiGo, easyJet, Wizz Air, Frontier, Spirit, JetBlue, Lufthansa, Air France, and Delta all fly LEAP-1A. The remaining 40% chose the Pratt & Whitney PW1100G geared turbofan.
COMAC C919
Sole engine on the C919. Launch customer China Eastern Airlines took first delivery in late 2022. Air China, China Southern, and other PRC carriers placed firm orders totalling around 300 airframes by 2025.

Frequently Asked Questions

How is LEAP more fuel-efficient than CFM56?

Three architectural changes: bypass ratio rises from 5-6:1 to around 11:1, the overall pressure ratio jumps from 32:1 to 40-50:1, and the fan and turbine adopt composite materials that cut weight by hundreds of pounds. Net result: around 15% lower fuel burn and 50% lower NOx versus the CFM56-7B at the same thrust. CFM publishes the comparison data on its LEAP programme page.

Why doesn't LEAP use a geared fan like the Pratt & Whitney PW1000G?

CFM judged that a direct-drive fan with composite blades could match the geared turbofan's fuel burn while avoiding the risk and weight penalty of a planetary reduction gear. The PW1000G runs the fan at around 4,000 RPM and the low-pressure compressor at around 12,000 RPM; LEAP runs both on a single shaft at around 3,800 RPM. Time will judge whether the geared or direct-drive bet ages better — both engines have hit reliability headwinds since service entry.

What was the 2018-2019 LEAP-1B durability problem?

Early LEAP-1B engines suffered premature wear on high-pressure-turbine blades and shrouds, especially in hot, dusty environments such as the Middle East and India. CFM redesigned the HPT components and rolled the fix into production by late 2019. The redesigned engines restored shop-visit intervals close to the 20,000-hour specification, though hot-and-sandy operators still see somewhat shorter intervals than benign-environment carriers.

How many LEAPs have been built?

CFM had delivered more than 5,000 LEAP engines by the end of 2025 across all three variants. The combined LEAP order book exceeds 10,000 firm orders — the largest backlog of any commercial engine programme ever — which sustains production through the 2030s at the planned rate of around 2,000 deliveries per year.

What is RISE?

RISE (Revolutionary Innovation for Sustainable Engines) is CFM's open-fan demonstrator, targeting entry into service around 2035 as the LEAP's successor. It removes the engine cowl entirely, with 12 counter-rotating composite fan blades spinning in open air at a 140-inch diameter. Goals include 20% better fuel burn over LEAP and full compatibility with 100% sustainable aviation fuel and hydrogen blends.

Is LEAP cleared to run on sustainable aviation fuel?

Yes. All LEAP variants are certified for up to 50% SAF blends today, and CFM has demonstrated 100% SAF operation on test engines. The 100% SAF certification path is on track for around 2030, paralleling the broader industry programme. The engine is also being tested with hydrogen as part of the Airbus ZEROe and CFM RISE demonstrator efforts.

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