Pick up the correct statement from the following: A. The speed of the aircraft relative to the ground, is called cruising speed B. The speed of the aircraft relative to wind, is called air speed C. When wind is blowing the direction of the flight, air speed is less than cruising speed D. All the above

The correct answer is D. All the above.

Cruising speed is the speed at which an aircraft flies when it is not accelerating or decelerating. It is typically the fastest speed at which an aircraft can fly for an extended period of time without damaging itself.

Air speed is the speed of an aircraft relative to the air around it. It is measured by an instrument called an airspeed indicator.

When wind is blowing in the direction of the flight, the air speed of the aircraft will be less than its cruising speed. This is because the wind is helping to push the aircraft forward.

When wind is blowing against the direction of the flight, the air speed of the aircraft will be greater than its cruising speed. This is because the wind is slowing the aircraft down.