Which of the following describes a tailwind?

A tailwind refers to wind that blows in the same direction that an aircraft is traveling. This means that if the wind is coming from behind the aircraft, it assists in the forward motion, resulting in an increase in ground speed and can lead to a shorter flight duration. Tailwinds are particularly beneficial during takeoff and landing as they can enhance an aircraft's performance, thereby enabling quicker accelerations during takeoff and possibly reducing landing distance.

The other types of wind mentioned in the incorrect options have distinct effects:

• Wind coming from the side of the aircraft is known as a crosswind, which can complicate handling, especially during takeoff and landing.

• Wind from the front of the aircraft is termed a headwind, which opposes the aircraft's travel direction, reducing ground speed and potentially increasing fuel consumption.

• Wind causing turbulence near mountains is often referred to as mountain wave turbulence, which results from wind interacting with the terrain, again affecting the flight but not relating to the concept of a tailwind.

Thus, describing the wind blowing from behind the aircraft accurately captures the essence of a tailwind's role in aviation.