What is the maximum operating speed (Vmo) when flying between 21,000 and 35,000 feet?

The maximum operating speed (Vmo) when flying in the altitude range between 21,000 and 35,000 feet is defined by Mach number rather than calibrated airspeed (KIAS). For the King Air 350, at these altitudes, the maximum operating speed is limited to 0.58 Mach. This designation is significant because as aircraft ascend, the relationship between indicated airspeed and Mach number becomes critical due to changes in air density and temperature.

Flying at excessive speeds in this altitude range could result in the aircraft exceeding structural limits or experiencing control difficulties. By defining Vmo as a Mach number in this particular altitude range, it ensures that pilots maintain safe operational limits as they ascend through altitudes where indicated airspeed can be misleading due to varying atmospheric densities.

Other choices provided refer to specific KIAS values, which are not applicable for that altitude band. The operational limitations for speed must consider aerodynamic effects that occur at subsonic speed, particularly in pressurized aircraft such as the King Air 350. Understanding these limits is crucial for maintaining safety and structural integrity during flight.