It works (in general, not sure about an airliner) because the virus does not travel in air. It travels only in small droplets of liquid, which can travel in air

It works (in general, not sure about an airliner) because the virus does not travel in air. It travels only in small droplets of liquid, which can travel in air, but only for short distances. On long distances those droplets just fall to the ground/surfaces. There are still precautions to take especially when touching surfaces, because the fallen droplets can then transfer onto the skin, and then later into the lungs when we touch our mouth, nose or eyes. But social distancing absolutely works in order to prevent the primary transfer of droplets from face to face through the air.