Are planes safe during COVID?

Hvac contractor here. Know this. Every public hallway ( looking at you apts and condos ) is positively pressurized, this is done to keep hallways safe in the case of fire. Your unit is at a lower pressure than the hallway. Meaning that the air from the hall IS going through your unit, especially if you have a window open or the bathroom fan on. If one person walks down the hall coughing then the is manhood chance if they walked past your door that the virus 8s entering your unit.   Also air filters almost never get changed on roof top units.. you can protect your unit by installing simple weather stripping around the door and at its base install a decent sweep..  stay safe.