Eagles, like other birds, flap their wings and give themselves thrust to move through the air and fly. The movements that create the lift are very similar to swimming motions.
There are four basic mechanics to eagle flight. The first is lift. Lift force is created by the action of air flow on the wing, which is known as an airfoil. The lift force occurs because the air pressure is higher below the wing and lower above the wing.
The second mechanic is gliding. Eagles obtain a mixture of forward and vertical force from their wings. This is due to the lift force being generated at a right angle.
One of the fundamental mechanics of bird flight is flapping. When a bird flaps, its wings continue to create lift. This constant lift is rotated forward to create thrust that counteracts drag and increases speed. The two stages of flapping are the down stroke, which provides most of the thrust, and the up stroke.
The final mechanic in bird flight is drag. The three major drag forces that impede upon a bird's flight are frictional, form and lift-induced drag.
Eagles have particularly large wings, which means they require more energy to fly. Because of this, eagles spend most of their time soaring and gliding as opposed flapping.