Wind's effects on the speed of an airplane include making the pilot increase his speed when the plane is flying into the wind. A plane flying directly into a headwind must compensate for the speed of the wind and increase the speed of the plane in order to arrive at its destination on time.
The opposite of a headwind is a tailwind. This refers to the situation in which the airplane is effectively being pushed forward by wind speed on top of its propulsion. In such cases, the pilot may need to decrease the speed of the airplane's propulsion if he wishes to maintain a certain speed.
The airplane's speed can sometimes be affected by wind drift as well. Wind drift refers to a situation in which wind blows from either the right or the left of the plane and can alter the plane's intended heading. Pilots must compensate for the drift by flying more in the direction opposite to the drift; for example, a pilot compensates for wind drift to the left by flying more towards the right. Since different winds can affect the airplane while it is turning to compensate for drift, the pilot is forced to adjust speed up or down as necessary.