Originally Posted by T/BE20/G

Most of the time, pilots have complete discretion over their speed within the operating limits of the airplane. Our dispatchers file a planned speed in our flight plan, but ATC doesn't normally comment even if our actual speed varies from the filed speed. There are times, however, that ATC does command speed. Usually, this would be during the low altitude arrival and departure phases of flight, particularly sequencing airplanes for arrival into major airports. It happens sometimes that speed restrictions (minimum or maximum) are issued in cruise, but not that often, relatively speaking.