What is the acceptable deviation for following ATC speed assignments?

• A. +/- 5 kts
• B. +/- 10 kts
• C. +/- 15 kts
• D. +/- 20 kts

Answer: (B)

The main idea is that when ATC gives you a speed, you’re expected to stay within a reasonable tolerance around that speed to keep traffic moving safely and predictably. The standard tolerance is plus or minus 10 knots. This means you should maintain your indicated airspeed within 10 knots faster or slower than the assigned value. This range accounts for wind changes, gusts, aircraft performance, and instrument lag, so controllers can rely on predictable spacing and sequencing. If conditions require you to be more than 10 knots off the assigned speed, coordinate with ATC and adjust as directed. Smaller or larger tolerances would either be too restrictive given real-world flight conditions or could degrade flow management.