High Quality Content by WIKIPEDIA articles! A lift jet is a jet engine angled to provide an aircraft with aerostatic (i.e. not requiring the movement of air over an airfoil) lift instead of (or in addition to) thrust. On a fixed-wing aircraft, lift jets may be installed as auxiliary engines, with a separate engine to provide forward thrust, or, as in the Harrier jump jet, may be vectored in flight to provide both.