Definition
An air traffic control instruction directing a pilot to increase the aircraft's airspeed to the specific value stated by the controller, and to maintain that speed until further advised.
Plain English
ATC is telling you to speed up to the exact number they give you, and hold that speed until they tell you to change it.
Context Anchor
Heard on the radio during arrivals, approaches, vectors, or other traffic sequencing when ATC needs aircraft spaced predictably.
Why Pilots Care
Following the assigned speed precisely keeps you properly spaced from other traffic. Drifting off the assigned speed can compress or stretch the sequence and force the controller to issue further corrections.
Intuition Check
Do not treat this as a casual suggestion to go a little faster. In ATC use, it is a specific speed instruction, but safety and aircraft limits still come first.
Example Sentence 1
Tower instructed us to increase speed to 250 knots, so I advanced the throttles smoothly and stabilized at that airspeed.
Example Sentence 2
During the climbout the instructor told the student to increase speed to best rate of climb.