The phrases
Core RT rules, phrase by phrase
Affirm, Negative, Roger, Wilco
These single-word replies help keep radio exchanges brief and clear. AFFIRM answers yes, while NEGATIVE answers no. ROGER confirms receipt without showing agreement. WILCO confirms both receipt and acceptance of an instruction.
Pilot
AFFIRM / NEGATIVE / ROGER / WILCO, [callsign]
ATC
[callsign], [acknowledgement or subsequent instruction]
ATC
Vistara 815, Hyderabad Radar, confirm flight level two six zero
Pilot
Affirm, flight level two six zero, Vistara 815
ATC
Vistara 815, expect radar vectors for an ILS approach to runway two seven
- To say yes on the radio, the standard word is AFFIRM. "Affirmative" is everyday speech, not ICAO phraseology, so avoid it.
- ROGER acknowledges reception but is not a substitute for a readback. Repeat clearance details accurately, including flight level, heading, speed, frequency, runway, squawk code, taxi clearance, hold-short instruction and QNH.
- WILCO conveys both receipt and agreement to follow an instruction. Saying "roger wilco" is redundant, so WILCO stands on its own.
Reference: ICAO Doc 9432 §2.6
Broadcast to All Stations
Use ALL STATIONS when you have information that every aircraft on the frequency needs and no single station is being addressed. You are telling the frequency what you are doing, not asking anyone for anything, so you do not wait for a reply. On an air-to-air or uncontrolled frequency this is how you keep everyone else's picture of you current.
Pilot
ALL STATIONS, [Callsign], [message]
ATC
[no individual reply expected. Any station that must act will answer]
Pilot
All stations, VT-AIR, westbound Bhopal VOR to Indore, leaving FL260 descending FL150
ATC
VT-AIR, Mumbai Control, roger
- Nobody has to answer an ALL STATIONS broadcast. Do not repeat it because the frequency stayed quiet. Only a station that must act will reply.
- Say ALL STATIONS first, then your callsign, then the message. Examiners listen for that order.
- Keep the message to what other aircraft can use: where you are, where you are going, and the level you are leaving or taking.
- ATC uses the same prefix in the other direction, for example an aerodrome closure or a general weather warning. When ATC broadcasts to all stations, you acknowledge only if the message asks you to.
Reference: ICAO Doc 9432
Cancel IFR Flight / Change to VFR
Use this declaration when the aircraft can remain in VMC and IFR control is no longer needed. It ends IFR separation service, while VFR clearances and airspace restrictions continue to apply.
Pilot
[station], [callsign], CANCELLING MY IFR FLIGHT, PROCEEDING VFR
ATC
[callsign], IFR FLIGHT CANCELLED AT [time], [squawk instruction]
Pilot
Kochi Approach, Alliance 912, cancelling my IFR flight, proceeding VFR
ATC
Alliance 912, Kochi Approach, IFR flight cancelled at zero two four five, squawk two thousand
Pilot
IFR cancelled at zero two four five, squawk two thousand, Alliance 912
- Cancellation is a pilot-initiated statement, not a request. Read back the cancellation time and the code ATC gives you. In India an aircraft with no assigned code squawks 2000, spoken two thousand (AIP India ENR 1.6, paragraph 13.7.1), not the 7000 used in Europe.
- You cannot return to IFR merely by asking. A fresh IFR clearance must be issued and accepted, and the applicable flight plan, entry and airspace conditions must also be met.
Reference: ICAO Doc 9432
File Airborne Flight Plan
Use this procedure when an aircraft must submit its flight plan after becoming airborne. Typical situations include extending a VFR flight beyond the original area or diverting to an aerodrome that was not listed beforehand. The responsible flight information service or aeronautical information centre receives the plan through voice communication.
Pilot
[station] [callsign] REQUEST FILE FLIGHT PLAN
ATC
[callsign] [station] PASS YOUR DETAILS
Pilot
Bengaluru Information, VT-KRA, request file flight plan.
ATC
VT-KRA, Bengaluru Information, pass your details.
Pilot
VT-KRA, Cessna 172, VFR, departed Hosur at zero four four five, direct Mysuru, four thousand five hundred feet, estimating Mysuru at zero six one zero, endurance three hours, three persons on board.
ATC
VT-KRA, Bengaluru Information, flight plan filed at zero five zero eight.
- Have the details ready before you call: callsign, aircraft type, flight rules, departure point and time, route, level, destination and estimate, endurance and persons on board. If the station wants them in another order, follow its lead.
- Record the exact clock time stated in the FLIGHT PLAN FILED reply. Enter it as the official filing time in the flight documentation.
Reference: ICAO Doc 9432
How Do You Read
Use this during an active two-way exchange when the pilot is unsure whether the controller's transmission came through clearly. Signs include a message that was not received, a weak response, or other transmissions interfering. Since the frequency is already in use for the conversation, it is not mentioned in this request.
Pilot
[station], [callsign], HOW DO YOU READ
ATC
[callsign], READING YOU [readability one to five]
Pilot
Bengaluru Control, IndiGo 5231, how do you read
ATC
IndiGo 5231, reading you four
Pilot
Roger, request flight level three seven zero, IndiGo 5231
- Both this check and RADIO CHECK use ratings one through five. Choose HOW DO YOU READ when a conversation is already in progress; choose RADIO CHECK when opening or confirming contact on a frequency.
- Omit the assigned VHF frequency from this request. The channel is understood during an established exchange, and adding its number may lead an examiner to regard the transmission as a RADIO CHECK.
- If two checks in succession both return a rating below three, treat reception as degraded. Inform the controller and coordinate a change to the alternate frequency before the link becomes unusable.
Reference: ICAO Doc 9432 §2.3 / §2.4
Numbers and callsign conventions
For every transmission containing callsigns, levels, headings, runways, frequencies or altimeter settings.
Pilot
[station you are calling], [callsign], [message with numbers].
ATC
[callsign], [message with numbers].
Pilot
Delhi Ground, Skyline 345, request taxi, information Charlie, QNH one zero zero nine.
ATC
Skyline 345, taxi via Alpha to holding point runway two niner left, QNH one zero zero nine.
Pilot
Taxi via Alpha to holding point runway two niner left, QNH one zero zero nine, Skyline 345.
- Transmit most numbers digit by digit: runway two seven, heading zero eight zero, squawk four two one three. Use HUNDRED for whole-hundred flight levels: flight level one hundred, flight level two hundred and flight level three hundred. Say other levels digit by digit, for example flight level one eight zero. Use THOUSAND for an altimeter setting or squawk code that is a whole thousand: QNH one thousand, squawk two thousand. Other settings and codes stay digit by digit, for example QNH one zero zero nine and squawk two four zero zero. A heading stays digit by digit even when it is a whole hundred: heading one zero zero. AAI MATS Part 1, Edition 7 (May 2025), paragraph 12.5.1 gives this rule. Do not say "three zero zero" for flight level three hundred: it is marked wrong.
- Say DECIMAL in a frequency, for example one two one decimal seven five zero.
- Keep your aircraft callsign at the end of a readback and at a point where identification matters.
- Use your assigned radiotelephony callsign every time. A registration may be used only where that is the assigned callsign.
Reference: ICAO Doc 9432, Chapter 2
QNH Read-Back
Every pressure setting you are given is read back. QNH sets your altimeter to read height above sea level, so a wrong figure puts the whole approach at the wrong altitude.
Pilot
QNH [value], [Callsign]
ATC
[Callsign], QNH [value]
ATC
VT-AIR, QNH 993 hectopascals
Pilot
QNH 993 hectopascals, VT-AIR
- QNH is always a read-back item, whether it arrived on its own or inside a longer clearance.
- Every digit is spoken separately, except a whole thousand. 1011 is one zero one one, 993 is niner niner tree, and 1000 is one thousand (AAI MATS Part 1, paragraph 12.5.1, Table 12-3).
- When the setting is below 1000, add the word HECTOPASCALS, so 993 goes out as QNH niner niner tree hectopascals and comes back the same way. The word is there so that a three figure value cannot be heard as an inches of mercury setting. Digit by digit and the added word are the same rule, not two competing rules.
- Indian AIP ENR 1.7 paragraph 1.3 says QNH is passed to the lower whole hectopascal, so you will never be given a decimal.
- A ten hectopascal error is roughly 280 feet of altimeter error, all of it in the dangerous direction when the real pressure is lower than the one you set.
- Source: ICAO Doc 9432 Manual of Radiotelephony, transmission of numbers, and ICAO Annex 10 Volume II Chapter 5 radiotelephony procedures.
Reference: ICAO Doc 9432
Radio Check
Conduct this check before departure, after selecting a new frequency, or if reception appears faulty. The pilot includes the current frequency so the ground station can verify that transmissions are being received on the intended channel.
Pilot
[station] [callsign] RADIO CHECK [frequency]
ATC
[callsign] [station] READING YOU [readability one to five]
Pilot
Goa Ground, SpiceJet 318, radio check one one eight decimal seven
ATC
SpiceJet 318, Goa Ground, reading you five
- Readability is assessed from one to five. One indicates an unreadable transmission, two means reception is intermittent, three is understandable with difficulty, four is clear, and five is perfectly clear.
- If the reported quality is below three, request another frequency rather than continuing with unreliable communication.
- Acknowledge the reply with ROGER and your callsign. The readability figure is information, not an instruction, so it does not need to be read back.
- Use RADIO CHECK when opening contact and state the selected frequency. For later checks after contact is established, use HOW DO YOU READ.
Reference: ICAO Doc 9432 §2.3
Read-Back of Clearance
Safety-critical ATC clearances must be repeated word for word so the controller can verify that all limits and instructions were received correctly. Read back clearance limits, routes, levels, headings, speeds, transponder codes, frequencies, runway assignments, taxi directions, hold-short instructions and altimeter settings.
Pilot
[repeat every required clearance item word for word], [callsign]
ATC
[callsign] [station], [clearance]. [callsign] READBACK CORRECT
Pilot
Kochi Delivery, Air India 447, stand one two, request clearance to Chennai via flight planned route
ATC
Air India 447, Kochi Delivery, cleared to Chennai via flight planned route, climb flight level two six zero, squawk six two four seven
Pilot
Cleared to Chennai via flight planned route, climb flight level two six zero, squawk six two four seven, Air India 447
ATC
Air India 447, readback correct
- Repeat each assigned detail exactly rather than summarising it. Use CLEARED AS FILED only when ATC issues that clearance; otherwise read back the route and flight level that were assigned.
- Finish the readback with your aircraft callsign. This identifies the aircraft whose clearance is being confirmed to the controller.
- On the first call the pilot names the station and gives the full callsign. Once contact is established the controller may leave out the unit name, which is why the final reply carries only the callsign.
- A spoken READBACK CORRECT confirms that the pilot repeated the clearance correctly. Silence is not confirmation, and the clearance remains in force until ATC amends or cancels it.
Reference: ICAO Annex 10 Vol II §5.2.1.7
Request Time Check
Use this request on the ground before departure or while airborne to verify the flight deck clock against UTC. ATC normally provides the minute; request half-minute precision only when needed.
Pilot
[station], [callsign], REQUEST TIME CHECK
ATC
[callsign], TIME [hours and minutes]
Pilot
Kochi Tower, IndiGo 5231, request time check
ATC
IndiGo 5231, Kochi Tower, time one three five eight
Pilot
Time one three five eight, IndiGo 5231
- ATC supplies Coordinated Universal Time, not local civil time. Pronounce every digit separately, for example, time zero six three zero.
- If seconds are required, add "and a half" after the minutes, for example, time one four two five and a half.
Reference: ICAO Doc 9432
Request Words Twice
Use this when interference or fading makes it hard to catch a clearance. WORDS TWICE asks the controller to send every word or group of words twice in the same transmission, so a word lost to noise the first time can be heard the second time.
Pilot
[station], [callsign], WORDS TWICE
ATC
[callsign], [each word or group of words sent twice]
Pilot
Bengaluru Control, Air India 447, words twice
ATC
Air India 447, Air India 447, descend flight level two four zero, descend flight level two four zero, QNH one zero zero six, QNH one zero zero six
- For weak reception, use WORDS TWICE instead of making repeated SAY AGAIN requests. This gets the key details repeated in one reply and avoids a string of extra transmissions.
- If your own signal is poor, give "I WILL SAY" followed immediately by "MY WORDS TWICE", then repeat the important message items.
Reference: ICAO Doc 9432
Say Again
Use it when an ATC message is unclear or incomplete and you need either the whole instruction or only the missing section repeated.
Pilot
[station], [callsign], SAY AGAIN [ALL AFTER / ALL BEFORE / BETWEEN] [reference]
ATC
[callsign], [station], [complete repeat or selected portion]
ATC
IndiGo 5231, climb flight level three five zero, contact Hyderabad Control one two one decimal three five
Pilot
Hyderabad Departure, IndiGo 5231, say again all after climb
ATC
IndiGo 5231, I say again, flight level three five zero, contact Hyderabad Control one two one decimal three five
- For a partial repeat, identify the dividing point: “say again all after [reference]”, “say again all before [reference]”, or “say again between [first reference] and [second reference]”.
- Requesting simply “say again” asks the controller to repeat the complete previous transmission.
- Overlapping transmissions can produce a continuous tone. Wait until the frequency is clear, then request anything that was missed.
Reference: ICAO Doc 9432
Speak Slower
Use this phraseology when an ATC transmission arrives too quickly for complete understanding. The need is especially common during brief instructions at busy airports. It is a safety measure, not a statement about the pilot's English, and controllers will usually repeat the information more clearly.
Pilot
SPEAK SLOWER, [callsign]
ATC
[callsign], ROGER, [message repeated more slowly]
ATC
IndiGo 5231, Bengaluru Control, cleared to Chennai via flight planned route, climb flight level two eight zero, squawk six four two three
Pilot
Speak slower, IndiGo 5231
ATC
IndiGo 5231, Bengaluru Control, roger, cleared to Chennai, flight planned route, climb flight level two eight zero, squawk six four two three
- Place your callsign after SPEAK SLOWER so the controller can identify the aircraft making the request.
- Ask for a reduced pace immediately rather than giving an inaccurate readback and requiring the controller to repeat the entire clearance.
Reference: ICAO Doc 9432
Standby
ATC uses this instruction when the pilot must wait because other traffic is being handled or further information is being obtained. It does not grant clearance for the requested action. The pilot should continue complying with the existing clearance and remain prepared for further communication. A pilot may also use STANDBY to postpone a reply until the required information is available.
Pilot
STANDBY, [callsign] (when the pilot needs time before answering)
Pilot
Kochi Control, IndiGo 5231, request descent to flight level two four zero
ATC
IndiGo 5231, Kochi Control, standby
- STANDBY does not authorise the requested manoeuvre. Continue to observe the clearance currently in effect and wait for an ATC clearance before acting on the request.
- If no further transmission arrives within approximately two minutes, use "[station], [callsign], confirm standby" to prompt the controller.
Reference: ICAO Doc 9432
Unable to Comply
Use this if an ATC instruction cannot be accepted safely, in accordance with regulations, or within aircraft capability. Common cases are a level above the certificated ceiling, a heading into hazardous weather, or a speed below the minimum safe for the current configuration.
Pilot
[station], [callsign], UNABLE [instruction] DUE [reason], REQUEST [alternative]
ATC
[callsign], ROGER, [revised clearance]
ATC
IndiGo 5231, Hyderabad Control, climb flight level four five zero
Pilot
Hyderabad Control, IndiGo 5231, unable flight level four five zero due performance, request flight level three eight zero
ATC
IndiGo 5231, roger, climb flight level three eight zero
- State which instruction cannot be met, give a concise reason, and include an alternative when possible. This gives the controller enough information to choose a safe replacement clearance.
- Notify the controller as soon as the limitation is known. Do not wait until the instructed action has begun, or continue it after declaring that you are unable.
Reference: ICAO Doc 9432
What you must read back
After every safety-related clearance or instruction.
Pilot
[callsign] readback of [route or instruction], followed by your callsign.
ATC
[callsign], [correction or readback check].
ATC
Skyline 345, climb flight level two hundred.
Pilot
Climb flight level two hundred, Skyline 345.
ATC
Skyline 345, correction, climb flight level two five zero.
Pilot
Climb flight level two five zero, Skyline 345.
- Always read back route clearances, runway entry, landing, take-off, backtrack, cross and hold-short instructions.
- Also read back runway in use, altimeter settings, transponder codes, level, heading, speed and transition-level instructions.
- Acknowledge other instructions so the controller knows you understood and will comply.
- If any part is unclear, say SAY AGAIN or CONFIRM. Never guess a number.
Reference: ICAO Doc 9432, 2.8.3
Practise a call
Say it out loud
The simulator runs the flight, two voices, on a clock.
YouAffirm, flight level two six zero, Vistara 815
ATCVistara 815, Hyderabad Radar, confirm flight level two six zero