AIM Text
The separate digits of the speed followed by the word “KNOTS.” Except, controllers may omit the word “KNOTS” when using speed adjustment procedures; e.g., “REDUCE/INCREASE SPEED TO TWO FIVE ZERO.”
The separate digits of the Mach Number preceded by “Mach.”
Source: FAA Aeronautical Information Manual · current edition · paragraph 4-2-11.
Research Notes
AIM 4-2-11 covers figures (numbers) pronunciation in ATC communications.
The pronunciation rules:
- Pronounce each digit individually: "two-three-zero" not "two-thirty." "One-two-zero-point-five" not "one twenty point five."
- Altitudes: "Climb to and maintain seven thousand" (full thousands) or "Climb to and maintain one-zero thousand" ("ten thousand" form). The combined form is acceptable for whole-thousand altitudes.
- Flight levels: "Flight Level three-five-zero" not "Flight Level three-fifty."
- Time: 24-hour Z-time pronounced as four digits: "One-five-three-zero Zulu." "Local time" usually expressed similarly.
- Frequencies: Each digit, with "point" or "decimal" for the decimal: "one-two-eight-point-five" or "one-two-eight-decimal-five."
- Heading: Three digits, no exceptions. "Heading zero-niner-zero" not "heading ninety."
- Squawk codes: Each digit individually. "Squawk one-two-zero-zero" not "twelve hundred."
Special cases:
- Runway numbers: digits individually ("runway two-seven left" or "runway zero-niner right")
- Altimeter setting: each digit ("two-niner-niner-two" for 29.92)
- Wind reports: "wind two-three-zero at one-five gusts two-five"
Reference: AIM 4-2-11; FAA Pilot/Controller Glossary.