What is best practice for reading back a speed or altitude instruction?

• A. Read back exactly, including all numbers and units.
• B. Read back only the numbers
• C. Read back the letters of the instruction
• D. Read back the instruction without numbers

Answer: (A)

Precise readback of speed or altitude instructions means stating the exact numeric value and the units. This matters because the numbers alone don’t carry the critical context of what they measure, and the units (feet versus meters, knots versus mph) tell you the intended quantity. Verifying the full phrase with both value and unit helps ensure the controller’s instruction is understood exactly as given and prevents miscommunication that could lead to an unsafe altitude or speed.

For example, if told to descend to 3,000 feet at 250 knots, you should reply with the whole instruction including “feet” and “knots.” Reading back only the numbers would leave out what those numbers refer to, and reading back without the units could cause confusion about the required quantity. Reading back just the letters or the instruction minus the numbers would omit the critical value entirely.