Originally Posted by lostinthegrid

The filtration isn't perfect and a recent systematic review of 15 studies shows that the risk increases with the length of the flight. However, wearing a mask pretty much negates the risk. Also risk varies with exposure time so taking your mask off to eat or drink increases the risk but it's still much lower than the risk of not being masked. You can get the study with details if you google "The Risk of Aircraft-Acquired SARS-CoV-2 Transmission during Commercial Flights: A Systematic Review" (I haven't posted enough to be able to post urls).