CFM International has received joint certification by US and European regulators of the Leap engine selected to exclusively propel the Boeing 737 Max family.

The type certificate approved by the European Aviation Safety Agency (EASA) and the Federal Aviation Administration (FAA) comes nearly three months after the 737 Max 8 achieved first flight.

Southwest Airlines plans to launch service with the 737 Max 8 in September next year, but some reports suggest the timeline could be accelerated to late 2016.

The Leap-1B represents the single-most important change among the design changes adopted by Boeing for the 737 Max family, accounting for an 15% reduction in fuel burn than the CFM56-7B it replaces.

“We couldn’t be happier with the way this engine is performing,” says CFM executive vice president Francois Bastin.

In March, CFM and Boeing officials announced that the Leap-1B had already met performance specifications, a slight acceleration from statements by both companies last summer insisting the fuel burn target would be achieved by entry-into-service.

The Leap-1A engine achieved type certification last November, paving the way for Airbus to deliver the first CFM-powered A320neo in mid-2016. The same approval by EASA and FAA also cleared the Leap-1C engine destined to power the Comac C919 in service. With the type certificate awarded to the Leap-1B, the GE Aviation and Snecma joint venture completes an eight-year development cycle.

So far, CFM officials have acknowledged making only one design modification through flight testing. A new abradable seal liner for the high-pressure compressor was replaced last fall.

The first Leap-1B engine entered ground testing nearly two years ago. Like its sisters powering Airbus and Comac models, the Leap-1B introduced ceramic matrix composites in the high-pressure turbine shrouds, a second-generation of the pre-swirl twin-annular combustor, a blisk fan in the compressor and fuel nozzles made using 3D printing.

It also differs from the single-stage turbine design of the CFM56, using a two-stage turbine to harness the power from the exhaust gases produced by the 120kN (28,000lb-thrust) turbofan. The fan diameter is also wider by about 20.3cm (8in), allowing more of the airflow to bypass the engine core, thus improving fuel efficiency. The airflow through the engine core is itself made more efficient, guided by a more advanced high-pressure compressor into the improved combustor.