Air vapor? Is it like liquid ice? ;)
This is called a condensation trail. It can be water droplets, just not because of boiling, but as a result of condensation - the reverse process of evaporation. Occurs when the local air temperature is lower than the ambient temperature. This can be seen in high humidity during takeoff and landing of an aircraft above and behind its wing.
Another type of plume - water crystals - occurs when the local temperature is higher than the ambient temperature. For example, behind the jet engines of high-flying aircraft.
When you press the clutch.
A white plume is air vapor generated at a certain air humidity when water boils from being heated by a jet of hot air emitted by a jet engine.