ATC phraseology glossary

Plain-English definitions of the radio terms you'll hear from ATC. 44 terms — search or scroll.

Acknowledge: Let ATC know you received and understood the message. A readback acknowledges; "roger" acknowledges receipt only.
Affirmative: Yes. Say "affirmative," not "affirm-itive" with extra syllables, and never just "yeah."
Air taxi: Helicopter movement above the surface (usually below 100 ft AGL) at speeds over about 20 knots — faster than a hover taxi.
Altimeter setting: The local barometric pressure (e.g. "two niner niner two") you set so your altimeter reads true altitude. Read it back digit by digit.
Approach: A radar facility (e.g. "Norcal Approach") that sequences and separates arriving and departing traffic near busier airports.
ATIS: Automatic Terminal Information Service — a recorded loop of weather and airport info, labeled by letter ("information Bravo"). Listen before you call.
Base leg: The pattern leg flown perpendicular to the runway, connecting downwind to final.
Class B: Airspace around the busiest airports. You need an explicit "cleared into the Class Bravo" before entering.
Class C: Airspace around moderately busy airports. Two-way radio contact (they say your call sign) is required to enter.
Class D: Airspace around a towered airport. Establish two-way radio contact with the tower before entering.
Clearance delivery: The ground position that issues IFR clearances (and some VFR departure instructions) before you taxi.
Cleared for takeoff: Authorization to depart on the specified runway. Always read it back with the runway and your call sign.
Cleared to land: Authorization to land on the specified runway. Read back the runway and your call sign.
Climb and maintain: Climb to and then level off at the assigned altitude. Read back the altitude.
CRAFT: A memory aid for an IFR clearance: Clearance limit, Route, Altitude, Frequency, Transponder.
CTAF: Common Traffic Advisory Frequency — the shared frequency pilots self-announce on at non-towered airports.
Discrete code: A unique four-digit transponder (squawk) code ATC assigns you, e.g. "squawk zero two three four."
Downwind: The pattern leg flown parallel to the runway, opposite the landing direction.
Expedite: Comply quickly. "Expedite your climb" means use a higher rate without delay.
Final approach: The last pattern leg, aligned with the runway, just before landing.
Go around: Abandon the landing and climb out. Fly the airplane first, then tell the tower or announce on CTAF.
Ground: The controller who manages taxiing aircraft on the movement area (taxiways and inactive runways).
Hold short: Stop before a runway or point and do not cross. Safety-critical — read it back verbatim, including the runway.
Hover taxi: Helicopter movement near the surface (in ground effect, generally below 25 ft) at slow speed.
Ident: Press the transponder IDENT button so your target flashes on the controller’s scope. "Squawk one two zero zero and ident."
IFR: Instrument Flight Rules — flight conducted under ATC control by reference to instruments, used in clouds and low visibility.
LAHSO: Land And Hold Short Operations — land and stop before an intersecting runway or point. Read back the hold-short.
Line up and wait: Taxi onto the runway and wait in position for takeoff clearance. Not a clearance to take off.
Maintain: Keep the assigned altitude, heading, or speed until told otherwise.
Mayday: The spoken distress signal for a life-threatening emergency, said three times: "Mayday, Mayday, Mayday."
Negative: No.
Pan-pan: The urgency signal (said three times) for a serious situation that is not yet a distress — one notch below Mayday.
Position and hold: Old phraseology for "line up and wait." Don’t use it; the current term is "line up and wait."
Readback: Repeating an ATC instruction back so the controller can confirm you heard it correctly. Required for clearances, runway assignments, and hold-shorts.
Roger: I received your last transmission. It does NOT mean yes, and it is not a substitute for a required readback.
Runway heading: Fly the magnetic heading of the runway centerline — do not turn after takeoff until told.
Say again: Repeat your last transmission. Use this instead of "what?" or "repeat" ("repeat" has a different meaning in some contexts).
Special VFR: A clearance to operate VFR in controlled surface-area airspace when weather is below basic VFR — you must request it and remain clear of clouds.
Squawk: Set this code on your transponder. "Squawk VFR" means set 1200.
Standby: Wait — I’ll get back to you. Don’t keep transmitting.
Tower: The controller responsible for the runways and the airport traffic pattern at a towered field.
Traffic in sight: You see the traffic ATC pointed out. If you don’t, say "negative contact" or "looking."
Unable: You cannot comply with an instruction. Say "unable" plainly and, if able, why.
Wilco: "Will comply." You received the message, understand it, and will do it. More than "roger."

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