1. Clean sky european research programmes, funded by the EU’s FP7 and HORIZON 2020 programmes. http://www.cleansky.eu/
2. International Air Transport Association (IATA), Airline industry economic performance, end-year report, December 2019. https://www.iata.org/en/iata-repository/publications/economic-reports/airline-industry-economic-performance---december-2019---report/
3. International Air Transport Association (IATA), Airline industry economic performance, mid-year report, June 2020. https://www.iata.org/en/iata-repository/publications/economic-reports/airline-industry-economic-performance-june-2020-report/
4. International Air Transport Association (IATA), Outlook for air travel in the next 5 years. https://www.iata.org/en/iata-repository/publications/economic-reports/covid-19-outlook-for-air-travel-in-the-next-5-years/
5. International Air Transport Association (IATA), What can we learn from past pandemic episodes? https://www.iata.org/en/iata-repository/publications/economic-reports/what-can-we-learn-from-past-pandemic-episodes/