The Rolls-Royce Trent 1000 Package B engine made its first flight on a production Boeing 787 on 24 September, confirmed programme vice president and general manager Scott Fancher.
Airplane 24, registered JA802A, will be the second 787 delivered to launch customer All Nippon Airways.
The Package B engine has been in flight testing on aircraft ZA004 and ZA002 since May, and is in its latter certification phases, Fancher said.
The 26 August FAA and EASA type certification included only the Package A Trent 1000 pairing with the 787.
The Package B engine incorporates a revised six-stage low pressure turbine (LPT) design, high-aspect-ratio blades, relocation of the intermediate-pressure (IP) compressor bleed offtake ports and fan outlet guide vanes with improved aerodynamics.
The updated engine will bring specific fuel consumption to within 1% of the original specification.
ANA and Boeing declined to comment on the delivery timing of the second 787 to ANA, though several program sources point a handover in the second half of October.
At June's Paris air show, Rolls-Royce expected ANA's fifth 787 to be powered by the Package B engine and would inaugurate international long-haul service, though ANA senior vice president Satoru Fujiki said the second aircraft will delivered in its short- to medium-haul configuration.