Physician and a pilot here... when you have test positivity rates of 10-15% as has been the case recently in much of the USA and Europe, it is simple math, statistics and epidemiology that would allow you to assume that you are carrying quite a few passengers who are carrying the virus on EVERY flight. Over time, this will be mitigated by an increasing percentage of the population that has relative immunity, either via vaccination or by natural immunity following an infection.