## 1 Introduction  
In Europe, there are approximately 448 airlines and 701 commercial airports that transported 606 million passengers during 2010 [1]. Air traffic has increased by a factor of 2.4 since 2000, and it was expected by pre-COVID-19 forecast an average increasing of 4.3% per year over the next 20 years [2]. Although the air transport sector has been strongly affected by the health crisis generated by the COVID-19, reducing the number of seats in 2020 by 50% [3], and the recovery of the sector will unfortunately not be immediate but expected between 2023 and 2025 [4], the long-term order forecast remains very important. For example, Boeing has a forecast of 48,400 aircraft by 2039 in October 2020, compared to 25,900 aircraft today [5], and the Airbus backlog stands at 7441 commercial aircraft at September 2020 compared to 7133 at the same point in last year [6], so efforts to optimize the sector's costs, and reduce fuel consumption and pollutant and greenhouse emissions, are still worthwhile. The cost of fuel is estimated at 32% of the operating cost of Airlines [7]. Besides, commercial aviation is currently responsible for about 2% of global carbon emissions, and about 12% of all COemissions from the transport sector and, it is estimated that CO\({}_{2}\) emissions from commercial aircraft may triple by 2050, with air transport emissions reaching 25% of the total [8]. On the other hand, passenger cars, pickup trucks, vans, motorcycles, and other two- and three-wheeled vehicles constitute about one-third of the world's demand for petroleum. They generate about half of all transport-related greenhouse gas emissions, produce carbon monoxide, non-combusted hydrocarbons, sulphur oxides, nitrogen oxides, particles, and other air toxins [8] and, a total of 2 billion vehicles are expected by 2030 [9]. The European Union (EU) has a clear commitment to a gradual replacement of fossil fuels by renewable energies. In December 2018, the Renewable Energy Directive 2018/2001/EU entered into force, which sets a new binding target for renewable energy in the EU for 2030 of at least 32% to become the first climate-neutral continent by 2050 [10]. In 2018, all airlines in the world with international routes began to officially report their emissions as part of the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), adopted by the United Nations in 2016, which aims to halve total carbon emissions by 2050 [11]. In June 2001, the Advisory Council for Aeronautics Research in Europe (ACARE) was created in Paris to develop and maintain a Strategic Research Agenda (SRA). This group consisted of the member states, the European Commission, and stakeholders from the aviation sector: the manufacturing industry, airlines, airports, service providers, regulators, research institutions, and academics. Among the goals defined for 2050 are a 75% reduction in CO\({}_{2}\) emissions per passenger and kilometer and a 90% reduction in NO\({}_{x}\) emissions. Additionally, air vehicles must be designed and manufactured to be recyclable [1]. Within this framework, and to meet current and future requirements, new innovative materials, design techniques, and manufacturing processes are being developed to increase efficiency and reduce consumption [11]. The new families of Airbus aircraft are engineered to optimize fuel efficiency, the A320 and A350 aircraft save more than 20% in fuel consumption. The A350 includes more than 50% lightweight structural materials, and the A220's primary structure includes aluminum-lithium on the fuselage, and titanium and hybrid materials on the wings [12]. For its part, the Boeing 737 MAX family uses 20% less fuel than the aircraft it replaces, and it is as efficient as a hybrid electric car in terms of liters of fuel equivalent used per 100 km and passenger [13]. The priorities defined in Boeing's environmental policy are, firstly, the reduction of CO\({}_{2}\) emissions in all activities and, secondly, the optimization of fuel consumption [11].