The PCR alone takes a couple of hours to run. Labs have significant turn around time because they're taking samples from various testing locations and running them centrally. Plus hardly anyone is running group testing. You swab everyone at boarding and run the test near the airport. For a transatlantic flight, the lab work will beat the plane every time. If you want to add on environmental testing we're looking at a quarantine several hours long at the point of arrival. There's growing evidence that saliva testing is reliable, so the procedure can be far less invasive than nasopharyngeal swabs.

And, yes, I agree. There are very few reasons anyone should be flying right now, mostly limited to "I need to be in place X or I will die."