If you are at 12,000 feet and told to descend to 8,000 feet and maintain 300 knots, is maintaining 300 knots still allowed?

• A. Yes, 300 knots is always allowed.
• B. No, the speed limit below 10,000 feet MSL is 250 knots.
• C. Yes, as long as you are above 10,000 feet.
• D. Only if ATC specifically clears you.

Answer: (B)

The main rule being tested is speed in relation to altitude: below 10,000 feet MSL, the maximum permitted speed is 250 knots indicated airspeed. In your scenario, you’re coming down from 12,000 feet to 8,000 feet. Once you descend below 10,000 feet, you must be at or below 250 knots. Therefore trying to maintain 300 knots would exceed the allowed limit during the portion of the descent below 10,000 feet.

If ATC had explicitly cleared you to exceed the limit (for example, to maintain 300 knots below 10,000 feet), then that clearance would override the general limit. But absent that explicit clearance, you must slow to 250 knots or less as you descend through 10,000 feet and below.