What factor affects indicated airspeed when flying at higher altitudes?

Indicated airspeed is directly influenced by the density of the air in which an aircraft is flying. As altitude increases, the air becomes less dense due to a decrease in atmospheric pressure and temperature. This reduced density affects the way the aircraft interacts with the air, leading to variations in the indicated airspeed.

Indicated airspeed, which is what a pilot sees on the airspeed indicator, is affected by the aircraft's speed relative to the density of the air. At higher altitudes, the lower air density means that the same true airspeed will result in a lower indicated airspeed reading. Thus, density is the key factor in understanding these changes in indicated airspeed at different altitudes.