An analysis of causal relation between daily commercial flights intensity and daily Covid-19 infections, in Croatia, during the 4th wave of Covid-19 epidemics

Effects of the Covid-19 pandemics have started to be identified in various socio-economic and technical segments and disciplines. Here a research and its results are presented in analysis of causality between two statistical variables: (1) daily number of new Covid-19 cases in Croatia, and (2) daily number of flights originated from or destined to Croatian airports, both during the period of the 4th wave of Covid-19 epidemics in Croatia (Quarter Four in 2021). Research methodology is devised that utilises Granger causality statistical test. The daily new Covid-19 case is identified as the target (effect) variable, of the daily number of flights in Croatia, as the predictor (cause) variable. Reversal of roles is found to have no causality. Additionally, it is found that cause will affect the target variable 1 – 4 days after the cause activation. Research results benefit a wide range of disciplines: from epidemiology, to flight planning and logistics.