The socio-economic benefits of air transport are significant, but so are the environmental costs. The aviation sector has experienced substantial growth in the past decades, resulting in increased emitted greenhouse gas emissions. Although the focus nowadays is to relaunch a global fleet of largely grounded aircraft, our environmental specialist, Asimina Voskaki believes we need to take a step back and think about how we can turn this into an opportunity for a green restart.

In this blog, Asimina Voskaki, Senior Manager and Environmental Lead at CAA International examines the primary considerations for aviation to emerge from the pandemic greener and more innovative.

Impact of aviation on climate change

Our desire to travel comes at a cost; aviation operations rely heavily on fossil fuel emitting gases and particles that change the atmospheric concentration of greenhouse gases and lead to contrail formation and increased cloudiness.

Aviation represents around 2.5% of global human-induced CO2 emissions. There are also non-CO2 impacts that lead to global warming. According to the International Committee on Climate Change (IPCC), aircraft contribute around 3.5% of the total anthropogenic radiative forcing.

Although today we have aircraft that are more environmentally efficient than decades ago, technological improvements have not been in line with the growth rate in air travel. Before the Covid-19 pandemic, the International Civil Aviation Organisation (ICAO) highlighted that emissions from international aviation could increase by 2050 two to four times the 2015 levels. In Europe alone, according to the European Union Aviation Safety Agency (EASA), CO2 and NOx emissions could increase by at least 21% and 16%, respectively, by 2040.

What is the sector doing to reduce greenhouse gas emissions?

To address the climate challenge, ICAO put together a basket of measures to meet the goals for 2% annual fuel efficiency improvement by 2050 and carbon-neutral growth from 2020 onwards. The European Union ratified the Paris Agreement and, with a set of policy initiatives (European Green Deal), aims to make Europe climate neutral by 2050. Under the Climate Change Act, the United Kingdom (UK) anticipates becoming a low-carbon economy and has committed to achieving net-zero carbon emissions by 2050.

How can aviation meet international environmental ambitions?

Aviation is hard to decarbonise compared to other sectors as it is heavily dependent on fossil fuels. Therefore, one of the main options is to enhance environmental efficiency by advancements in the design and technology of aircraft and engines. This option has provided considerable benefits so far as today’s aircraft can be up to 80% more efficient in the use of fuel per passenger kilometre than in the 1960s.

The recent developments in electric or hybrid-electric aircraft technology (e.g. zero-carbon emission aircraft concepts, zero-carbon emission energy sources, etc.) indicate that although there are challenges, it can be technically possible to achieve net-zero carbon emissions. Several research and innovation projects are already being implemented globally to explore the possibilities of zero-carbon emission aircraft. For example, the UK launched the FlyZero initiative to support the UK aerospace sector in developing a zero-carbon emission aircraft by 2030.

While some innovative environmentally driven technologies and energy sources are promising, it may take long before they can enter the market and be fully commercialised. As science, research, and innovation are fundamental to the decarbonisation of aviation, we need suitable frameworks in place that support technology innovation and expertise to drive forward low carbon innovation.

The modernisation and improvements to airspace efficiency and the optimisation of air traffic management and operational procedures, like the optimised continuous climb and continuous descent operations, carbon-efficient ground movements, can also significantly reduce greenhouse gas emissions. These measures benefit airports, airlines, passengers and communities living around airports as they can achieve fewer delays and reduced levels of noise and emissions.

The use of sustainable aviation fuel could be the key to achieve carbon-neutral growth. It is estimated that a 32% reduction in emissions by 2050 could be gained from sustainable aviation fuel in the UK. Although they can act as an intermediate step to technologies like hybrid-electric and all-electric aircraft, the use of these fuels are currently minimal and may take time for these fuels to be deployed at scale cost-efficiently, and ensuring the environmental integrity of the production. Some airlines, technology developers and fossil fuel companies have started investing in sustainable aviation fuels. Currently, six bio-based aviation fuel production pathways have been certified by EASA. While ongoing initiatives aim to increase market penetration, one of the main barriers is the price compared to fossil-based kerosene.

As technological, operational measures or sustainable aviation fuels cannot address the carbon-neutral growth objective fully, ICAO introduced a global offsetting programme, the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA). CORSIA is an instrument that complements the existing initiatives by offsetting the amount of CO2 emissions that cannot be reduced. ICAO estimates that by 2035 the sector would need to offset around 2.5 billion tonnes of CO2 emissions to achieve carbon-neutral growth. The pilot phase of CORSIA started on 1 January 2021 on a voluntary basis. 88 ICAO Member States have volunteered to monitor, report, verify and offset CO2 emissions based on the requirements set by ICAO.

Requirements to progress environmental initiatives post COVID-19

As the aircraft take to the skies and aviation operations resume, we need to centre environmental commitments in all aviation activities to reshape the global aviation system. Leading a green recovery offers the chance to emerge from the pandemic with improvements to aviation safety, security, technology, efficiency, and making air transport sustainable for future generations.

The question is whether we have what it takes to deliver these ambitious plans. Decarbonisation plans should be based on robust and flexible policies to tackle aviation emissions by assessing a range of measures that could be implemented in the short, medium and long term. They should also enable the establishment of frameworks supported by investments to facilitate innovation and technological progress. Consideration should also be given to how best to support staff to develop skills and capabilities needed to transition to a climate-neutral aviation sector. Everyone has a role to play, and behaviour change is the key to success.

Environmental advice and training

To support National Aviation Authorities and the aviation industry organisations in addressing the impact of aviation on climate change, we offer advisory services and a suite of training courses, covering noise management, modelling and contouring, climate change mitigation and adaptation, ICAO CORSIA advice and implementation and environmental impact and assessment.

If you would like to discuss how CAAi can support you and your organisation in improving your environmental performance, please email To discuss or book your place on our training courses, please email

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