In 2013, Snecma announced that they planned to use the A340 as a flying testbed for the development of a new open rotor engine. This test aircraft is forecast to conduct its first flight in 2019. Open rotor engines are typically more fuel-efficient but noisier than conventional turbofan engines; introducing such an engine commercially has been reported as requiring significant legislative changes within engine approval authorities due to its differences from contemporary jet engines. The engine, partly based on the Snecma M88 turbofan engine used on the Dassault Rafale, is being developed under the European Clean Sky research initiative.