Definition
An air traffic control instruction directing a pilot to slow the aircraft to a specific airspeed stated by the controller. The phrase is used in radio communication, with the actual numerical speed inserted in place of the second word 'Speed' (for example, 'Reduce speed to 210').
Plain English
ATC is telling you to slow down to an exact speed they will say out loud. You then fly at that speed until told otherwise.
Context Anchor
Heard on ATC radio calls during approach, arrival, departure, or traffic spacing when controllers need aircraft moving at specific speeds.
Why Pilots Care
Compliance maintains safe separation from other aircraft and satisfies published speed restrictions.
Intuition Check
Do not treat “reduce speed to” as a casual suggestion to slow down generally. In this context, it is a specific ATC instruction: slow to the stated speed and hold it, unless safety requires otherwise or ATC changes the instruction.
Example Sentence 1
Approach radioed, 'Cessna 32 Charlie, reduce speed to 110,' and the pilot pulled the throttle back to slow the aircraft.
Example Sentence 2
The tower cleared us to reduce speed to 160 knots on final approach.