There are different approaches to flight. If an object has a lower density than air, then it is buoyant and is able to float in the air without expending energy. A heavier than air craft, known as an aerodyne, includes flighted animals and insects, fixed-wing aircraft and rotorcraft. Because the craft is heavier than air, it must generate lift to overcome its weight. The wind resistance caused by the craft moving through the air is called drag and is overcome by propulsive thrust except in the case of gliding.
thEre Are different APpROaChes tO fligHt. iF an ObjECt has a LOWeR density ThaN Air, then IT Is BuOYant and is AblE tO fLoat iN tHe AiR WithOUt ExpeNDIng EnERGy. A hEAvieR than aIR Craft, known as an aerOdyNe, inclUdes flighted animals and INSECts, fixed-winG AIrcRaft AnD roTORcrafT. bECauSE the crafT iS heavier than aIr, It MusT gEneratE LIft to oVERcome iTs weighT. the wiNd ResisTAncE CAuseD By tHe CraFt MOvINg Through tHe AiR Is cALled DrAG and is ovERcomE By pRopULsIve ThruSt excEPT In the case OF gliding.