for those of you interested this vortex is not created by the plane's engines. As we know the aerofoil cross section of the plane's wings creates a differential pressure across the top and bottom of the wing, an area of high pressure on the bottom of the wing and an area of low pressure on top of the wing, creating the lift which enables flight. As we also know if we have two area's of differential pressure then they will try to reach an equilibrium pressure by the substance in the high pressure zone flowing to the low pressure zone. This is what is happening to create the vortex. The high pressure air under the wing flows around the tip of the wing to the low pressure zone above the wing gaining momentum as it flows and swirling behind the plane as a vortex. These wing tip vortices consume a lot of energy in their creation, stealing this energy from the plane (creating drag) hence making the plane less efficient (consume more fuel). This is why large airliners have vertical "winglets"