If only we used masks all the time in public: “A jet airliner with 54 persons aboard was delayed on the ground for three hours because of engine failure during a takeoff attempt. Most passengers stayed on the airplane during the delay. Within 72 hours, 72 per cent of the passengers became ill” … with flu. In 1979. We’ve had so much time.

“An outbreak of influenza aboard a commercial airliner”
M R Moser et al. Am J Epidemiol. 1979 Jul. https://pubmed.ncbi.nlm.nih.gov/463858/