A significant part of aeronautical science is a branch of dynamics called aerodynamics, which deals with the motion of air and the way that it interacts with objects in motion, such as an aircraft.
When you pour a liquid from one container to another, the liquid takes the shape of the container. The volume of the liquid is the same. The properties that solids and liquids share are that they both have definite volume.
Solids have a definite shape and a definite volume. Liquids have more kinetic energy, so their particles are less rigid and can slide around one another, which allows liquids to flow. Liquids have no definite shape, so that they take the shape of their container, except for the surface, which is flat, but they do have a definite volume. Gases have more kinetic energy than liquids, so their particles move very rapidly. Gases expand to fill their container, so they have no definite shape and no definite volume.