When holding at altitudes above Flight Level 310, what is the minimum speed allowed per the SOP?

• A. Mach .70 or Driftdown Speed, Whichever is higher
• B. Mach .65
• C. Mach .75
• D. 0.70 Mach

Answer: (A)

When holding at high altitudes, you must keep a minimum airspeed that prevents a stall while still giving you enough maneuvering capability. Mach 0.70 acts as a safe baseline at altitude, but the aircraft’s driftdown speed—the speed you’d maintain while descending safely if needed—can be higher depending on weight and configuration. The SOP requires you to use the higher of these two speeds, so you’re never slower than what the aircraft safely tolerates in either ordinary holding or a potential descent scenario. That’s why the correct approach is to use Mach 0.70 or the driftdown speed, whichever is higher. The fixed lower speeds don’t account for the potential to need a higher speed for safe control, and a single fixed speed would be unsafe in some conditions.