Definition
ATC-issued speed instructions given to an aircraft during descent to manage spacing, sequencing, or traffic flow into a terminal area. Pilots are expected to comply with the assigned speed, advise ATC if unable, and may not deviate from it without clearance.
Plain English
When you're descending, controllers can tell you to fly faster or slower so they can fit you into the traffic flow. You fly the speed they give you, and if you can't, you tell them.
Context Anchor
You may hear or see descent speed adjustments during arrival planning, while following air traffic control instructions, or when flying a published arrival route into a busy airport.
Derivation
“Descent” comes from older words meaning “to climb down.” “Adjust” means to bring something into a better fit. Together, the term points to changing speed while coming down so the aircraft fits into the traffic flow.
Why Pilots Care
These adjustments prevent traffic conflicts and keep the arrival flow moving efficiently without vectoring or holding.
Intuition Check
Do not read “adjustment” as a casual suggestion. In this context, it is a speed change that must be followed when assigned, unless you cannot safely comply.
Example Sentence 1
On the descent into Atlanta, ATC issued a speed adjustment of 250 knots to maintain spacing behind the preceding traffic.
Example Sentence 2
The pilot complied with the descent speed adjustments by increasing the rate of descent to 2,000 feet per minute until established on the approach.