>>9798483For the flies to not fall, they have to push down with 0.5kg of force and hope the air below them stays there. For the air below them to stay there, it has to push down with 0.5kg of force.
If the air below them doesn't stay there, then them pushing down with 0.5kg of force is equivalent to a guy jumping in a falling elevator.
If the air below them doesn't stay there, they end up with a vortex ring state and fall down.