How soon before reaching an assigned holding fix should pilots begin to slow to the assigned holding speed?

Pilots should begin to slow to the assigned holding speed three minutes before reaching the assigned holding fix to ensure they can stabilize their airspeed and maintain control of the aircraft while preparing to enter the holding pattern. This time allows sufficient opportunity for the airplane to decelerate gradually, helping pilots avoid abrupt speed changes that could complicate the approach into the hold.

By commencing the slowdown three minutes in advance, pilots can also account for any variations in their flight path due to air traffic control instructions or environmental factors such as wind, ensuring a safe transition into the holding maneuver. This practice aligns with standard operating procedures that prioritize safety and efficiency in flight management.