Modern jet engines cut commercial aircraft fuel burn by up to 15 percent over predecessors

Advancements in jet engines continue to be the primary force behind increasing the fuel efficiency of commercial aircraft. While aerodynamic enhancements and materials improvements contribute, engine technology remains the dominant factor in reducing fuel consumption. Airlines, which face high fuel bills and pressing carbon reduction targets, benefit significantly from the latest generation of engines that combine power with improved efficiency.

Jet engine technology has evolved through several types, starting with turbojets that compress and burn air to produce thrust, followed by turboprops where the turbine drives a propeller for better fuel economy at slower speeds. The most widespread commercial application today is the turbofan engine, which uses a large front fan to push some air around the engine core via a bypass duct. The bypass ratio—the amount of air bypassing the core relative to the air passing through—has increased dramatically, enabling higher thrust with less fuel burned.

The Boeing 737 series illustrates the efficiency gains through engine evolution. Early 1960s 737-100/200 models ran on Pratt & Whitney JT8D low-bypass turbofans. Later 737 Classic aircraft incorporated the higher bypass CFM56-3, cutting fuel burn nearly 20 percent below JT8D levels. The Next Generation 737NG then adopted the CFM56-7B, which improved fuel consumption by 8 percent over the Classic's powerplants through refinements in core design, aerodynamics, and fan blade technology.

The most recent Boeing 737 MAX fleet exclusively features the CFM LEAP-1B engine. This state-of-the-art turbofan delivers a further 15 percent specific fuel consumption reduction compared to the CFM56-7B, thanks to a core influenced by the General Electric GEnx engine, increased composite materials usage, and substantially higher bypass ratios.

Beyond narrow-body aircraft, widebody engines have also seen notable efficiency gains. General Electric’s transition from the CF6 to the GEnx engine for the Boeing 787 and 747-8 series brought about approximately 15 percent fuel savings by doubling bypass ratio and adopting advanced materials and aerodynamic improvements. Further advances are visible in the Boeing 777 series, where the first-generation GE90 was succeeded by the cutting-edge GE9X for the 777X. The GE9X integrates technologies from the GEnx and features extensive ceramic matrix composites, achieving around 10 percent better fuel burn than the GE90.

While fuel efficiency is paramount, engine operators also weigh maintenance costs and durability. Some promising engines like Rolls-Royce’s Trent 1000 and Pratt & Whitney’s PW1000G have encountered challenges meeting durability expectations, resulting in higher maintenance needs. In contrast, the CFM LEAP and General Electric’s newer engines have maintained strong reliability records, contributing to their commercial success.

The interplay between bypass ratio, fan size, engine weight, and core temperatures defines each engine’s efficiency profile. Higher bypass ratios generally improve fuel economy but come with aerodynamic drag and weight penalties. Manufacturers are pushing materials science boundaries, using composites and CMCs to reduce weight and allow higher operating temperatures, which lower fuel burn. General Electric’s GE9X exemplifies this approach, achieving a 60:1 overall pressure ratio, enabling remarkable efficiency gains.

These continual improvements in engine technology not only reduce airlines’ fuel costs but also play a key role in global efforts to decarbonize aviation. The industry aims for carbon neutrality by 2050, and advancements like those seen in the LEAP-1B and GE9X engines are critical steps forward in mitigating the environmental impact of air travel.