“…For that reason, the International Air Transport Association (IATA), for instance, strives to improve fleet-wide fuel efficiency by 1.5% p.a. from 2009 to 2020, cap net emissions from 2020 (carbon-neutral growth) and reduce net emissions by 50% until 2050, relative to 2005 levels [1,5]. As a consequence, airlines are forced to modernize their fleet either by replacing old aircraft or by retrofitting new fuel-efficient airframe and engine technologies (e.g., blended winglets, geared turbofan) into existing aircraft of the fleet [6,7].…”