Which instrument indicates the speed of an aircraft?

The airspeed indicator is the instrument specifically designed to measure and display the speed of an aircraft relative to the surrounding air. It provides crucial information about how fast the aircraft is moving, which is essential for safe flight operations, especially during takeoff, landing, and various flight maneuvers.

The reading on the airspeed indicator is usually displayed in knots or miles per hour. Understanding airspeed is vital for pilots, as it influences control and performance, including lift, drag, and fuel efficiency.

The other instruments serve different purposes: the altimeter measures the altitude of the aircraft above sea level, the attitude indicator shows the orientation of the aircraft relative to the horizon, and the vertical velocity indicator indicates whether the aircraft is climbing or descending and at what rate. Each of these instruments is important for overall flight management, but none provides information on the speed of an aircraft like the airspeed indicator does.