Aside from incidental, auxiliary loads, in level flight the principal load on the aircraft propulsion engine is the power required to provide the continuous lift. To construct an exergy flow diagram for an aircraft – for example, for the purpose of pinpointing inefficiencies and for costing – an expression is needed for the exergy delivered to and by the wings. That is, an expression is needed for the exergy of lift. The purpose of this paper is to present an expression developed for the exergy of lift, applicable not only in level flight but in other modes of flight as well. In order to illustrate the relevance of exergy of lift, two exergy flow diagrams are presented for a light aircraft, one for level flight, and one for climb.