Walkaround

Engines · CFM International

LEAP

LEAP-1A, LEAP-1B, LEAP-1C

in production 3 min read · updated 11 October 2026 · checked 11 October 2026

Turbofan model under test
An ultra high bypass ratio turbofan model in a NASA wind tunnel. Credit NASA.

At a glance

Engine card

VariantsLEAP-1A, LEAP-1B, LEAP-1C
ArchitectureTwo shaft turbofan, bypass ratio around 11:1
Thrust24,500 to 35,000 lbf
ApplicationsA320neo family, 737 MAX, COMAC C919
Built byCFM International, the GE Aerospace and Safran joint venture
StatusIn production

Program and production

The LEAP is the highest volume engine programme in commercial aviation, and the story of the past two years has been durability rather than output.

Early LEAP engines did not hold time on wing in hot, dusty environments. Fine sand ingested in the Middle East, India and parts of Africa clogged the film cooling holes in the high pressure turbine stage 1 blades, which then ran hotter than designed and degraded quickly. Operators in those regions were removing engines far earlier than the business case assumed.

CFM's answer came in two steps. The LEAP-1A received regulatory approval for more durable high pressure turbine blades first. The LEAP-1B followed, with the FAA and EASA certifying the full durability kit in July 2026.

CFM is industrialising production of the new hardware now, targeting full production cutover early in 2027. That timing matters to operators: until cutover, new deliveries can still carry earlier standard hardware, so the configuration of an incoming engine is worth confirming rather than assuming.

Technical and maintenance

The durability kit is not a single part. Engineers redesigned the stage 1 blade, the stage 1 nozzle and the forward inner nozzle support together.

In plain terms

The high pressure turbine sits directly behind the combustor, in the hottest gas in the engine. Its blades are cooled by air bled through tiny holes in the blade surface, which forms a film of cooler air over the metal. Block those holes and the cooling film fails.

The new stage 1 blade uses revised internal cooling geometry so that fine sand particulates pass through rather than accumulating and blocking the film cooling apertures. The reinforced nozzle structures address circumferential warping caused by intense thermal gradients. CFM reports the redesigned blades held structural integrity for twice as long as the original product, and describes the effect as doubling time on wing in the harshest operating environments.

On the line

The gain is concentrated in hot and harsh operations. An operator in northern Europe will see less benefit than one in the Gulf or on Indian domestic sectors, so do not apply a single expected interval across a mixed network. During the transition, track which engines carry kit hardware and which do not, because the two populations will behave differently and mixing them in one reliability average will hide the picture.

Applications and fleet

The LEAP-1A competes directly with the Pratt and Whitney PW1100G on the A320neo family, and the LEAP-1B is the sole engine on the 737 MAX. The LEAP-1C powers the COMAC C919.

That sole source position on the MAX means LEAP supply is tied directly to Boeing's single aisle output, which has been constrained by Boeing's own wing production rather than by engines. On the A320neo, the contrast with GTF groundings has made LEAP the lower risk choice in the eyes of many operators, and engine selection on new orders has reflected that.

Safety

No significant developments since 11 October 2026.

The durability work described above is a reliability and cost matter rather than a safety one. No Airworthiness Directive of fleet wide significance was issued against the family in this period.

Sources