This glossary is written for virtual airline and flight simulation use within Virtual Air Canada Airline. It is not intended as a real-world aviation reference.
VMO
Maximum Operating Speed
VMO is the maximum indicated airspeed (IAS) at which an aircraft is permitted to operate in normal flight. It is defined in the Aircraft Flight Manual (AFM) and represents the upper boundary of the aircraft’s certified operating envelope with respect to airspeed. Exceeding VMO risks structural damage from aerodynamic loads and flutter. On modern transport aircraft, VMO is typically around 340-350 knots IAS and applies at lower altitudes where the IAS-to-Mach relationship means airspeed rather than Mach number is the limiting factor. Above a transition altitude, the limit switches to MMO (Maximum Operating Mach number), and the aircraft’s speed must stay within both limits at all times.
On the airspeed indicator and PFD speed tape, VMO is depicted as a red and white striped pointer or “barber pole” that moves as atmospheric conditions change, marking the boundary of the safe operating band. Modern aircraft are equipped with automatic overspeed protection - on Airbus fly-by-wire types the envelope protection prevents the pilot from commanding speeds beyond VMO/MMO, while Boeing aircraft use an autothrottle clamp and aural warnings. In a dive or steep descent, airspeed can build rapidly, and energy management is critical to staying within the VMO/MMO envelope. Some aircraft also have a structural speed VMO/MMO reduction for flight in turbulence, known as the turbulence penetration speed (VB or Vturbulence).