Here is an interesting study published on a rate of transmission of COVID-19 on the 4 hr international flight with 7 people boarded the plane with positive result for Coronavirus.
https://jamanetwork.com/journals/jamanetworkopen/articlepdf/2769383/hoehl_2020_ld_200137_1596736851.26276.pdf
https://jamanetwork.com/journals/jamanetworkopen/articlepdf/2769383/hoehl_2020_ld_200137_1596736851.26276.pdf