The effects of the Covid-19 output on the air transport industry and investigation of its effects on selected airline companies operating in the world

The aviation industry is extremely sensitive to the effects arising from global economic, social and political developments as well as due to operational weaknesses and financial weaknesses within its structure. The Covid-19 epidemic, which started in Wuhan, China in late 2019, affected the entire world. The fact that air transport is a type of fast transport and offers the possibility of intercontinental transfer has increased the spread of Covid-19 in wider geographical regions. With the spread of the epidemic, economic activities related to global trade declined, causing air transport operations to decline. In line with World Health Organization (WHO) recommendations, countries initially restricted air transportation to protect themselves from the contagious effect of Covid-19, then closed their borders and banned most of their flight activities. These developments caused a decrease in the revenues of the aviation sector and an increase in financial losses in other sectors related to the aviation sector. In this study, the financial performance of selected airlines was examined before and during the Covid-19 period through multi-criteria Decision Making methods using ratio analysis. In this case, the quarterly financial permanence of 12 airlines for the period 2017-2021 was also examined. The Extended Entropy method was used to determine the levels of significance of the criteria used in the study while the TOPSIS method was used to rank the performance of airlines. The financial performance status of these companies has been revealed.