In colloquial usage, air is used for meaningless. If someone tells me that I am air to him or her, it is not positive, but means: I am not interested in you at all. Air is also not visible and hardly perceptible. However... if we are travelling fast enough, we feel the air resistance. Depending on the surface of attack, this can be considerable in combination with the wind. So air is not nothing or insignificant. But it doesn't bother us as long as we are in normal operation, so to speak. Only when things get fast and hectic does it become perceived as a brake or resistance. Actually, in many cases for the better. Who knows how much we would otherwise overdo it with speed and endanger ourselves and others. Perhaps this also applies in a figurative sense: if you stay in your healthy operating mode, it's good. If you are above it, the resistance is a warning in a positive sense.