Radio fundamentals
How any radio call is built: spelling and numbers, callsigns, the four-part call, what you must read back, the standard words, who to call in each class of airspace, squawk codes, ICAO differences and how MSFS 2024's ATC menu maps to real calls. Phase-by-phase calls are in VFR towered, VFR untowered, IFR departure, IFR en route and arrival and emergencies.
Call structure
Every call answers four questions, in this order (AIM 4-2-3). Listen before you key the mic, and know what you'll say before you press it.
| Part | What to say | Example |
|---|---|---|
| 1. who you're calling | facility name + type | "Palo Alto Ground" |
| 2. who you are | full callsign on first contact | "Skyhawk one two three alpha bravo" |
| 3. where you are | ramp or taxiway on the ground; distance and direction from a landmark, plus altitude, in the air | "at the terminal ramp" / "one zero miles south, three thousand five hundred" |
| 4. what you want | the request, plus the ATIS letter if there is one | "with information Charlie, request taxi" |
| Call type | Format | Notes |
|---|---|---|
| first contact with a facility, or a new controller | all four parts | if the frequency is busy, call with parts 1 and 2 only and wait for "go ahead" |
| replying to ATC | readback or answer, then your callsign | "Runway three one, cleared for takeoff, Skyhawk three alpha bravo" |
| follow-up request on the same frequency | callsign + request, facility name optional | "Skyhawk three alpha bravo, request right downwind departure" |
| check-in after a handoff | facility, callsign, altitude (and "climbing to …" or "descending to …") | ATC already knows who you are |
Facility types (AIM table 4-2-6): "… Clearance Delivery" (or "… Clearance"), "… Ground", "… Tower", "… Departure", "… Approach", "… Center", "… Radio" (Flight Service), "… UNICOM" (airport radio), "… Traffic" (self-announce on a CTAF).
Callsigns
| Situation | Say | Rule |
|---|---|---|
| first call to any facility or controller | "Skyhawk one two three alpha bravo" | type or maker, then the registration without the N (AIM 4-2-4) |
| after ATC shortens it | "Skyhawk three alpha bravo" | type + last three characters; only after ATC does it first |
| similar callsign on the frequency | full callsign again | ATC stops abbreviating both aircraft (7110.65 2-4-15) |
| student pilot | add "student pilot" on first contact | ATC gives extra help (AIM 4-2-4) |
| airline | "United Twenty-Five Heavy" | group-form numbers, plus "heavy" or "super" if it applies |
ATC may call you "Cessna" instead of "Skyhawk": answer with the callsign they use.
Phonetic alphabet and numbers
| Letter | Word | Letter | Word | Letter | Word |
|---|---|---|---|---|---|
| A | Alfa | J | Juliett | S | Sierra |
| B | Bravo | K | Kilo | T | Tango |
| C | Charlie | L | Lima | U | Uniform |
| D | Delta | M | Mike | V | Victor |
| E | Echo | N | November | W | Whiskey |
| F | Foxtrot | O | Oscar | X | X-ray |
| G | Golf | P | Papa | Y | Yankee |
| H | Hotel | Q | Quebec (keh-BECK) | Z | Zulu |
| I | India | R | Romeo |
| Digit | US practice | AIM table / ICAO pronunciation |
|---|---|---|
| 0 | zero | ZEE-RO |
| 1, 2 | one, two | WUN, TOO |
| 3 | three | TREE |
| 4 | four | FOW-ER |
| 5 | five | FIFE |
| 6, 7, 8 | six, seven, eight | SIX, SEV-EN, AIT |
| 9 | niner | NIN-ER |
| decimal | "point" | "decimal" (ICAO; the FAA accepts it, AIM 4-2-8) |
Everyone says "niner" (it can't be confused with the German "nein"). "Tree" and "fife" are in the AIM table but you'll rarely hear them in the US; they're standard in ICAO countries.
Saying numbers
| Item | Written | Spoken | Source |
|---|---|---|---|
| altitude below 18,000 ft | 3,500 / 12,500 | "three thousand five hundred" / "one two thousand five hundred" | AIM 4-2-9 |
| round altitude over 9,900 ft | 10,000 | "one zero thousand" (ATC may also say "ten thousand") | AIM 4-2-8 |
| flight level, 18,000 ft and up | FL190 | "flight level one niner zero" | AIM 4-2-9 |
| heading | 050 | "heading zero five zero" (always three digits, magnetic) | AIM 4-2-10 |
| wind | 310° at 12 G18 | "wind three one zero at one two gusts one eight" | 7110.65 2-4-17 |
| altimeter | 30.02 | "altimeter three zero zero two" | 7110.65 2-4-17 |
| frequency | 118.6 / 135.275 | "one one eight point six" / "one three five point two seven" (ATC drops digits after the second decimal) | 7110.65 2-4-17 |
| squawk code | 4521 | "squawk four five two one" | AIM 4-1-20 |
| runway | 31, 17L | "runway three one", "runway one seven left" | 7110.65 2-4-17 |
| time | 1845Z | "one eight four five Zulu" (Pacific daylight: add 7 h) | AIM 4-2-12 |
| speed | 90 kt | "niner zero knots" | AIM 4-2-11 |
| airway | V12 | "Victor Twelve" | AIM 4-2-8 |
| traffic position | 2 o'clock, 3 NM | "traffic two o'clock, three miles, eastbound" | AIM 4-1-15 |
VFR cruising altitudes above 3,000 ft AGL (14 CFR 91.159): magnetic course 0–179° → odd thousands + 500 ("five thousand five hundred"); 180–359° → even thousands + 500. You'll state one when asking for flight following.
Readbacks
Read back with your callsign every time (AIM 4-4-7). Read altitudes and headings in the order ATC gave them. If unsure, read back what you heard: ATC will correct it.
| Instruction | Read back? | Example readback | Source |
|---|---|---|---|
| hold short of a runway | required: ATC must get it ("read back hold instructions" if you skip it) | "Hold short runway three one, Skyhawk three alpha bravo" | AIM 4-3-18; 7110.65 2-4-3, 3-7-2 |
| runway assignment in a taxi clearance | yes, with left/right/center | "Runway three one, taxi via Zulu, Skyhawk three alpha bravo" | AIM 4-3-18, 4-4-7 |
| line up and wait | yes | "Runway three one, line up and wait, Skyhawk three alpha bravo" | AIM 4-3-18 |
| cross or enter a runway | yes | "Cross runway one two at Alpha, Skyhawk three alpha bravo" | AIM 4-3-18 |
| takeoff or landing clearance | yes, with the runway | "Runway one seven right, cleared to land, Skyhawk three alpha bravo" | AIM 4-4-7 |
| land and hold short (LAHSO) | full readback incl. "hold short of …" | decline if you can't stop in the distance | AIM 4-3-11 |
| altitude or altitude restriction | yes | "Climb and maintain five thousand five hundred, Skyhawk three alpha bravo" | AIM 4-4-7 |
| heading (vector) | yes | "Left heading two seven zero, Skyhawk three alpha bravo" | AIM 4-4-7 |
| frequency change | acknowledge; repeating the frequency is good practice | "One two five point two five, Skyhawk three alpha bravo" | AIM 4-2-3 |
| squawk code | common practice | "Squawk four five two one, Skyhawk three alpha bravo" | AIM 4-4-7 |
| IFR clearance | full readback | see IFR departure | AIM 4-4-7 |
| altimeter, wind, traffic, information | acknowledge; the altimeter readback is optional in the US | "Three zero zero two, Skyhawk three alpha bravo" / "Looking, Skyhawk three alpha bravo" | AIM 4-4-7 |
Charted altitudes in procedures aren't read back unless ATC states them (AIM 4-4-7).
Key phrases
| Phrase | Meaning | Use it when |
|---|---|---|
| "roger" | I received your last transmission | acknowledging information; never as a yes or no |
| "wilco" | I received it, understand and will comply | an instruction with no numbers to read back |
| "affirmative" / "negative" | yes / no (or "not correct") | answering a question; ICAO says "affirm" |
| "unable" | I can't comply | a clearance would break a rule or exceed the airplane; add the reason |
| "say again" | repeat your last transmission | you didn't catch it; "say again all after …" for part |
| "standby" | wait, I'll call you back | not an approval or a denial; don't act on it |
| "go ahead" | send your message | ATC's answer when you only gave your callsign |
| "request …" | I'd like … | any request: "request flight following", "request taxi" |
| "cleared …" | you may proceed as stated | takeoff, landing, Class B, IFR; ATC never says "cleared to taxi" |
| "expect …" | plan on this, don't do it yet | "expect runway one seven right" |
| "radar contact" | ATC sees and has identified you | flight following or IFR service has started |
| "radar service terminated" | services end; usually with "squawk VFR, frequency change approved" | leaving flight following |
| "resume own navigation" | vectors are over; navigate yourself | after vectors or when radar contact is lost |
| "traffic in sight" | I see the traffic you called | reply to a traffic call |
| "looking" | I don't see it yet, still looking | common reply; not in the P/CG |
| "negative contact" | I didn't see it, or couldn't reach a facility | traffic you never saw; add "request vectors" if needed |
| "say intentions" / "advise intentions" | tell me what you plan to do | answer with your plan: "request full stop", "remain in the pattern" |
| "verify …" / "confirm …" | check this | "verify assigned altitude five thousand five hundred" |
| "immediately" / "expedite" | act now / hurry | collision or runway conflict; comply first, talk after |
| "contact" vs "monitor" | call on the new frequency / just listen there | "monitor tower" means don't call |
| "have numbers" | I have wind, runway and altimeter only | not the same as having the ATIS |
| "correction" | my last words were wrong, here's the right version | fixing your own call mid-transmission |
| "speak slower" / "words twice" | slow down / say each phrase twice | poor reception or a fast controller |
| "with you" | informal check-in | common but not standard; give your altitude instead |
ATIS, AWOS and ASOS
| Service | What it is | Where you find it | How to report it |
|---|---|---|---|
| ATIS (Automatic Terminal Information Service) | recorded airport info (wind, visibility, sky, temperature, altimeter, runway in use, notices) with a letter code; new letter on every update | towered airports; Chart Supplement, sectional box, EFB | "with information Charlie" on first contact with ground, tower or approach (AIM 4-1-13) |
| D-ATIS | the same, also sent as text by datalink | larger airports | same |
| AWOS / ASOS (automated weather) | one-minute-updated weather, machine voice, no letter code | many untowered airports; broadcast within about 25 NM below 10,000 ft (AIM 4-3-27) | "I have the Lincoln one-minute weather" |
| "have numbers" | runway, wind and altimeter only, e.g. from UNICOM | anywhere | "have numbers" (never means you have the ATIS) |
Listen to the ATIS before first contact: about 20–30 NM out inbound, and before taxi outbound. If the letter changes while you're on the frequency, ATC will usually tell you ("information Delta now current").
Who to call by airspace
Contact rules only (14 CFR 91.126–91.135, AIM 3-2); ceilings and shapes are on the chart.
| Class | Before you enter, VFR | Who you talk to | Transponder |
|---|---|---|---|
| A (18,000 ft MSL to FL600) | IFR only | Center | Mode C + ADS-B Out |
| B (busiest airports) | a clearance: hear "cleared through / to enter Bravo airspace" | Approach on the charted frequency; Clearance Delivery when departing the primary airport | Mode C + ADS-B Out, also within the 30 NM Mode C veil |
| C (busy airports) | two-way radio contact: ATC answers with your callsign | Approach on the charted frequency; Tower when departing the primary | Mode C + ADS-B Out, inside and above it up to 10,000 ft |
| D (towered airports) | two-way radio contact: ATC answers with your callsign | Tower | none required |
| E (controlled, no tower) | nothing for VFR | optional flight following with Approach or Center | Mode C + ADS-B at 10,000 ft MSL and above (except at or below 2,500 ft AGL) |
| G (uncontrolled) | nothing | self-announce on the CTAF at untowered airports | none required |
"Two-way radio contact" means ATC replied using your callsign: "Skyhawk one two three alpha bravo, standby" counts; "aircraft calling, standby" does not, and neither does "remain outside" (AIM 3-2-4, 3-2-5).
Transponder and squawk codes
A transponder (squawk) answers radar with a 4-digit code and, in Mode C, your pressure altitude. ADS-B Out also broadcasts GPS position. Keep both on, altitude reporting enabled, on every movement area (AIM 4-1-20).
| Code / instruction | Meaning | What you do |
|---|---|---|
| 1200 | VFR, not talking to ATC | default VFR code; "squawk VFR" means go back to 1200 |
| ATC-assigned (e.g. 4521) | you're identified with ATC | set it, read it back |
| 7500 | unlawful interference (hijack) | only if it applies |
| 7600 | radio failure | see lost comms |
| 7700 | emergency | see emergencies |
| 7777 | military interceptors only | never select it |
| 1202 / 1255 | VFR glider / firefighting aircraft | not for the Skyhawk |
| "ident" | press IDENT once | only when ATC asks |
| "squawk standby" / "squawk normal" | transponder to STBY / back on the same code | as told |
| "stop altitude squawk" | turn off altitude reporting | also check your altimeter setting |
When changing codes, don't pass through 75xx, 76xx or 77xx: for 2700 → 7200 go via 2200 (AIM 4-1-20).
ICAO differences
What changes when you fly outside the US (ICAO Doc 9432; UK CAP 413 edition 24 as the worked example).
| Topic | FAA (US) | ICAO / UK |
|---|---|---|
| digits | "three, four, five", "niner" | "tree, fower, fife, niner", "tousand" |
| decimal | "point" | "decimal" |
| frequencies | "one three five point two seven" (drops a 3rd decimal) | all six digits: "one one eight decimal one two five" |
| altimeter | inches of mercury: "altimeter two niner niner two"; readback optional | hectopascals: "QNH one zero one three" (QFE, height above the field, in some places); readback required |
| flight levels | FL180 and up everywhere | transition altitude varies by country and airport, often far below 18,000 ft; ATC gives the transition level |
| round flight levels | "flight level two zero zero" | UK: "flight level two hundred" |
| level instructions | "climb/descend and maintain five thousand" | "climb/descend to altitude five thousand feet" or "to flight level eight zero" |
| yes | "affirmative" | "affirm" |
| reply to a call-up | "go ahead" | UK: "pass your message" |
| taxi | "Runway three one, taxi via Alpha" (crosses taxiways, not runways) | "taxi to holding point Alpha One, runway two seven"; UK uses "hold short" only where no holding point exists |
| line up | "Runway three one, line up and wait"; conditional line-ups aren't allowed | "line up and wait" or "line up"; conditional allowed: "behind the landing A320, line up and wait behind" |
| after landing | taxi past the hold line; tower may say "contact ground" | "report vacated", "runway vacated" |
| "take-off" | used in the takeoff clearance | used only in the takeoff clearance (or its cancellation); "departure" elsewhere |
| radar | "radar contact" | "identified" |
| mandatory readbacks | hold short, runway, altitude, heading, clearances | also altimeter settings, squawk codes, frequency changes, type of service, transition level |
| VFR code | 1200 | 7000 in most ICAO states (UK "conspicuity") |
| VFR radar service | flight following | UK Basic Service / Traffic Service; ICAO flight information service |
| callsigns | "Skyhawk one two three alpha bravo" → "Skyhawk three alpha bravo" | "Golf Alpha Bravo Charlie Delta" → "Golf Charlie Delta" (first + last two) |
| no tower | CTAF, "Palo Alto traffic" | UK: an air/ground station with the callsign "(airfield) Radio", or SAFETYCOM 135.480 |
MSFS ATC
MSFS 2024's built-in ATC is a menu: you pick a numbered request, the sim speaks your call and readback, and a controller voice answers. It follows your filed flight plan and the COM frequency you're tuned to.
| Real procedure | In MSFS 2024 | Note |
|---|---|---|
| ATIS before first call | tune the ATIS or AWOS frequency and listen | note the letter yourself and use it in your spoken practice call |
| full calls in your own words | choose from the panel options | practice by saying the call aloud before you click |
| readback | the sim reads back for you | real ATC listens for mistakes; the sim can't |
| handoff to a new frequency | acknowledge in the panel, then tune the new frequency yourself | auto-tune from MSFS 2020 is missing in 2024 (reported) |
| CTAF self-announce | announcement options when tuned to the CTAF at an untowered field | missions penalize "entered runway without announcement" (release notes 1.2.7.0) |
| turning off automatic calls | the AI Radio Communications (ATC) assistance setting | if left on, the sim may call and acknowledge for you; found under Assistance → Piloting (reported) |
| callsign | set the tail number and callsign in the aircraft's customization before the flight | ATC voices the callsign you set (reported) |
| Known quirk | Status |
|---|---|
| a flight plan filed as VFR still prompts for an IFR clearance | (reported) Nov 2024–Jul 2025 on the official forums |
| VFR clearance denied in visually clear weather | fixed in 1.2.7.0 (Dec 2024) |
| ATC broken after a takeoff without clearance | fixed in Sim Update 5 (Apr 2026) |
| takeoff clearance option missing when the hold-short line is close to the runway | fixed in the Sim Update 7 beta (Sep 2026) |
| phraseology and instructions that differ from the 7110.65 | expected: treat this sheet, not the sim, as the standard |
For live or AI controllers that understand free speech: VATSIM (free, volunteer ATC), PilotEdge (subscription, FAA-style ATC), BeyondATC and SayIntentions.AI (AI ATC add-ons).
Recipes
Any first call
Fill the four slots; drop the ones that don't apply.
"<Facility>, <full callsign>, <where you are>, <with information X>, <request>."
"Palo Alto Ground, Skyhawk one two three alpha bravo, at the terminal ramp,
with information Charlie, VFR to Sacramento International, request taxi."
"NorCal Approach, Skyhawk one two three alpha bravo, one five miles southwest
of Sacramento International, four thousand five hundred, with information Echo,
landing Sacramento International."Checking in on a new frequency
After "contact NorCal Approach one two five point two five": read it back, switch, listen a few seconds, then call.
YOU One two five point two five, Skyhawk three alpha bravo.
(switch, listen until the frequency is quiet)
YOU NorCal Approach, Skyhawk one two three alpha bravo, four thousand five hundred.
ATC Skyhawk three alpha bravo, NorCal Approach, altimeter three zero zero two.
YOU Three zero zero two, Skyhawk three alpha bravo.Climbing or descending: "… three thousand two hundred, climbing to four thousand five hundred."
When you didn't catch it
Never guess at an instruction. Ask for exactly the part you missed.
YOU Skyhawk three alpha bravo, say again.
YOU Skyhawk three alpha bravo, say again the altitude.
YOU Skyhawk three alpha bravo, say again all after "turn left".
YOU Skyhawk three alpha bravo, verify heading two seven zero?
ATC Skyhawk three alpha bravo, affirmative, heading two seven zero.If you're not sure the call was for you: "Was that for Skyhawk three alpha bravo?"
Correcting a wrong readback
ATC answers a wrong readback with "negative" and the correct version. Read the correction back in full.
ATC Skyhawk three alpha bravo, climb and maintain five thousand five hundred.
YOU Climb and maintain four thousand five hundred, Skyhawk three alpha bravo.
ATC Skyhawk three alpha bravo, negative, climb and maintain five thousand five hundred.
YOU Five thousand five hundred, Skyhawk three alpha bravo, sorry.Traffic call
Answer every traffic call. Say "looking" until you see it, then "traffic in sight".
ATC Skyhawk three alpha bravo, traffic eleven o'clock, four miles, southbound,
a Cherokee, three thousand five hundred.
YOU Looking, Skyhawk three alpha bravo.
YOU Traffic in sight, Skyhawk three alpha bravo.
or, once it's passed without a sighting:
YOU Negative contact, Skyhawk three alpha bravo.Declining an instruction
Say "unable" and why, then offer what you can do.
ATC Skyhawk three alpha bravo, climb and maintain six thousand five hundred.
YOU Unable, clouds above, Skyhawk three alpha bravo can maintain four thousand five hundred.References
- FAA Aeronautical Information Manual, Basic with Change 3 (July 9, 2026) (opens in a new tab): ch. 4 sections 1–4 for contact procedures, numbers, readbacks, ATIS, transponder use; ch. 3 section 2 for airspace entry
- FAA Pilot/Controller Glossary (opens in a new tab): meaning of every standard word, from "roger" to "resume own navigation"
- FAA Order JO 7110.65BB, Air Traffic Control (opens in a new tab): what controllers say; ch. 2 section 4 for readbacks, numbers and callsigns
- 14 CFR part 91 (opens in a new tab): 91.126–91.135 airspace communication rules, 91.159 VFR cruising altitudes, 91.215 transponders
- UK CAA CAP 413, Radiotelephony Manual, edition 24 (opens in a new tab): ICAO-style phraseology as used in the UK; readback list, numbers, taxi and line-up phrases
- MSFS 2024 release notes: 1.2.7.0 (opens in a new tab), Sim Update 5 (opens in a new tab): ATC fixes
- MSFS forums: ATC forcing IFR when filing VFR (opens in a new tab): the VFR-to-IFR quirk (reported)
- VATSIM (opens in a new tab), PilotEdge (opens in a new tab), BeyondATC (opens in a new tab), SayIntentions.AI (opens in a new tab): networks and add-ons with voice ATC