1. The great lockdown: worst economic downturn since the Great Depression, IMF, 2020. https://blogs.imf. org/2020/04/14/the-great-lockdown-worst-economic-downturn-since-the-great-depression/.
2. COVID-19: Outlook for air travel in the next 5 years, IATA, 2020, https://www.iata.org/en/iata-repository/publications/economic-reports/covid-19-outlook-for-air-travel-in-the-next-5-years/.
3. Effects of novel coronavirus (COVID-19) on civil aviation: economic impact analysis, ICAO, 2020. https:// www.icao.int/sustainability/Documents/COVID-19/ ICAO_Coronavirus_Econ_Impact.pdf.
4. The impact of COVID-19 (coronavirus) on aviation, CIRIUM. https://www.cirium.com/thoughtcloud/visualization-impact-coronavirus-aviation/.
5. COVID-19 impact on the European air traffic network, Eurocontrol, 2020. https://www.eurocontrol.int/covid19/.