Our world is facing unprecedented environmental challenges. Keeping the global temperature rise below 1.5°C implies a mandatory drop in CO2 emissions. Against this backdrop, the EC has issued the European Green Deal: an ambitious plan towards a fully sustainable economy, including aviation. With one million species endangered, biodiversity restoration is another key issue. Once aviation has recovered from the COVID pandemic effects, global air traffic as a major enabler of connectivity and economic growth will resume and keep increasing. This emphasizes the challenge of reducing the environmental impact of the air transportation sector as a whole. OLGA partners (airports, airline, handler, industry, research, SMEs) unite a wealth of expertise to contribute to solving this complex challenge: efficient and carbon neutral airport and airline operations, sustainable logistics, smart energy & mobility, intermodality for passengers and freight, emission/air quality assessments, green construction and circular end-of-life solutions. Sustainable Aviation Fuels supply chains will be integrated in conventional jet fuel infrastructure. Complementary types of low-emission mobilities, electric ground support equipment, hydrogen infrastructure and reduced carbon airside operations will be demonstrated. OLGA will achieve significant quantified advances already within the first three years, ready for exploitation by partners. This will lead to proven CO2 reduction, air quality improvement and biodiversity preservation with involvement of the entire sector's value chain. Sustainable impacts will be realised on societal, environmental and economic levels at local, national and EU scale. OLGA will have a duration of 60 months, requesting a 25 MEuros grant. OLGA's airports are uniquely positioned to showcase the environmental innovations, while the airports of Zagreb and Cluj will prove scalability and EU-wide applicability.