Radiotelephony phraseology: the key standard phrases between pilot and controller

You are standing at the fence with the tower in your ear: “Lufthansa four two seven, wind two six zero degrees eight knots, runway two six right, cleared to land.” Then all that comes back is “Cleared to land two six right, Lufthansa four two seven” – and a minute later the jet touches down in front of you. If you know radiotelephony phraseology, you hear the complete workings of an airport in these terse sentences. This guide explains the key standard words, the structure of a transmission, the rules for reading back and typical phrases from pushback to landing.

Radiotelephony phraseology: the short answer

Phraseology is the fixed vocabulary of aviation radio. Every standard word has exactly one meaning, every transmission a fixed order, and safety-relevant instructions are read back word for word. That way a Brazilian pilot and a German controller understand each other without follow-up questions even through noise and under time pressure.

The rules come from the International Civil Aviation Organization, ICAO: Annex 10 (Volume II) describes the radio procedures, Doc 4444 (PANS-ATM) the air traffic control phrases, and the manual Doc 9432 explains the practice. In the EU, the rules are binding through Regulation (EU) No 923/2012, SERA for short. Many aviation authorities also publish their own manuals that supplement the ICAO framework nationally. For you as a spotter, this means: what you learn at one airport you will understand at almost any other too.

How a transmission is built

The initial call always follows the same pattern: first the station called, then the caller, then the message. So a pilot does not check in with “Hello, this is …” but, for example, like this: “Munich Tower, Lufthansa four two seven, established ILS two six right.” The controller answers the other way around, with the aircraft’s callsign first.

In crew replies, the own callsign comes last: “Climb flight level one two zero, Lufthansa four two seven.” That way the controller instantly knows who is acknowledging – important when several similar callsigns are on one frequency. Why callsign and flight number are not the same is explained in the article Callsign vs. flight number; the post Airline callsigns and their history collects quirky airline callsigns.

A few basic principles apply to every transmission:

• Think first, then press. The frequency is a shared medium. Whoever transmits blocks everyone else.
• Do not talk over others. If two stations transmit at the same time, the signals overlap and both messages are lost. That is exactly what swallowed a crucial warning at Tenerife in 1977.
• Short and complete. Courtesies drop out, numbers and units stay in.
• Ask when in doubt. “Say again” or “Confirm …” is always better than guessing. A readback made on a hunch, in the hope of being corrected, counts as poor practice.

The key standard words

The heart of phraseology is the standard words. They look like English but are technical terms with an exactly defined meaning. The following table shows the ones you hear most often at the airport:

Standard word	Meaning	Typical situation
Acknowledge	Confirm that you have received and understood the message	Controller wants to be sure that information arrived
Affirm	Yes	Answer to a controller’s question
Negative	No, not permitted or not correct	Refusing a request, negation
Roger	Last transmission received in full – nothing more	Acknowledging traffic information or weather
Wilco	Understood, will comply	Acknowledging an instruction without a readback requirement
Approved	The requested action is approved	Answer to a request, such as for engine start
Cleared	Clearance under the stated conditions	Takeoff clearance, landing clearance, route clearance
Confirm	Please confirm …	Controller or pilot wants to verify a detail
Correction	Error – the right version follows	Slip of the tongue in mid-transmission
Disregard	Ignore	A previous transmission is void
Contact	Establish contact with …	Handoff to the next frequency
Monitor	Listen on … without calling	Switch to a frequency without an initial call
Standby	Wait, I will call you	Controller is busy at the moment
Unable	Cannot comply	Crew declines an instruction, usually with a reason
Say again	Please repeat	Transmission not understood or only partly understood
I say again	I repeat	Controller stresses or repeats a detail
Report	Report …	“Report established on the localizer”
Request	I ask for …	Crew asks for altitude, direct routing or a runway
Break break	Separates transmissions to different stations	Busy frequency, controller addresses several aircraft
Words twice	Each word twice	Very bad connection

Numbers, letters and how they are pronounced

In the noise, digits quickly sound alike. That is why fixed pronunciations apply: tree for 3, fower for 4, fife for 5 and niner for 9. Thousand is spoken “tousand,” and the point in frequencies is “decimal.” Letters go through the spelling alphabet from Alfa to Zulu – all the details are in the article ICAO spelling alphabet and number pronunciation.

As a rule, numbers are spoken digit by digit. How a number sounds depends on the context, however:

Item	Example	How it sounds on the radio
Flight level	FL 120	“flight level one two zero”
Altitude	4,000 ft	“four thousand feet”
Heading	090 degrees	“heading zero niner zero”
Transponder code	4721	“squawk four seven two one”
Air pressure	1013 hPa	“QNH one zero one tree”
Runway	26R	“runway two six right”

For transponder codes, each digit is spoken individually, whereas for altitudes “thousand” and “hundred” are used. What the codes mean and which special cases exist is covered in the articles on squawk codes 7500, 7600 and 7700 and on the Mode S transponder.

Readback: what has to be read back

The readback is the most important safety loop in aviation radio. The crew repeats the safety-relevant parts of an instruction word for word, the controller listens and corrects if something is wrong. If the controller overlooks an incorrect readback, it is called a hear-back error – the aircraft may then fly to an altitude that was never cleared.

Under the ICAO and SERA rules, the following are read back, among others:

• route clearances
• clearances and instructions to enter a runway, land on it, take off from it, hold short of it, cross it or backtrack on it
• the active runway, altimeter settings and transponder codes
• instructions on altitude, heading and speed, as well as transition levels

Other transmissions such as traffic information or general advisories are usually acknowledged by the crew only with Roger or the callsign. Whether a frequency handoff is read back is regulated slightly differently by country – in practice you almost always hear it repeated.

A flight on the radio: from the gate to landing

Phraseology gets most exciting when you follow a flight through all its phases. The following examples are simplified and use an invented flight number, but they show the typical sequence. Numbers and frequencies are purely example values.

For step 1, take a look at the article ATIS explained: the letter tells the controller that the crew knows the weather and the active runway. What departure and arrival routes mean is covered under SID and STAR, and how the precision approach works is explained in the guide to the ILS approach. If you hear “hold at …”, it is time for the article on holdings and holding patterns.

Conditional clearances and other subtleties

Some phrases sound harmless but are precisely calibrated. A good example is the conditional clearance. At busy airports it saves time: “Lufthansa four two seven, behind the landing A320 on short final, line up runway two six right and wait, behind.” The condition comes first, the aircraft it refers to is described exactly, and at the end the condition is briefly repeated. The crew reads the whole thing back, condition included – so nobody lines up in front of the wrong aircraft.

Other subtleties you can listen for:

• Hold position: The instruction simply means: stay where you are. You hear it, for example, when the tower has to stop a takeoff before the aircraft starts rolling.
• Hold short: “Hold short of runway …” means stopping before the runway. This too is always read back.
• Expect: “Expect ILS approach runway …” is planning information, not a clearance.
• Report: With “report …” the controller asks for a call at a point or in a given state, such as “report established.”
• Cancel takeoff: If a takeoff clearance is canceled, it is one of the few moments when the word takeoff comes up again.

Why it is so strict: the lessons of Tenerife

Many rules seem pedantic until you know their history. In the 1977 accident at Tenerife, two Boeing 747s collided on the runway and 583 people died. Several communication problems came together: the route clearance contained the word “takeoff,” the crew read it back with an unclear phrasing, the tower answered with a plain “OK,” and a warning was lost in a simultaneous radio transmission. The whole story is told in the article on the Tenerife air disaster of 1977.

As a result, standard phrases and English as a common working language were emphasized more strongly. An “OK” as acknowledgment is no longer enough, key parts of an instruction must be read back, and the word takeoff is reserved for the takeoff clearance. Since the 2000s, ICAO has also required formal proof of English proficiency at Level 4 or higher on its rating scale for pilots and controllers in international traffic.

Later incidents have sharpened phraseology further as well. One example: in 2016 ICAO standardized the phrases for departure and arrival routes after ambiguous altitude clearances on SIDs had repeatedly caused problems. How air traffic control as a whole has grown is described in the post History of air traffic control.

Phraseology as a tool at the spot

For you as a spotter, the radio is a kind of preview of the next few minutes. A few phrases are especially worthwhile:

• “Cleared to land” on your runway: now it is time to raise the camera.
• “Line up and wait”: someone is about to take off – often enough for a taxi shot at the threshold.
• “Going around”: A go-around brings unusual perspectives and usually a second approach.
• “Runway in use” and wind reports: they tell you whether you are standing at the right end. More on this in the guide Understanding runway direction at airports.
• “Mayday” or “Pan pan”: emergencies and urgency calls – background in the article Mayday and Pan-Pan. The rule here: listen, do not spread it.

How to get access to the radio in the first place is explained in the articles Understanding aviation radio frequencies, Listening to aviation radio online and Buying an aviation radio scanner. Before you start, be sure to read the post on the legal situation of listening to aviation radio: in Germany, not everything that is technically possible is allowed, and passing on what you hear is a topic of its own.

At big airports like Frankfurt Airport or Munich Airport there is a lot going on on the frequencies, which makes practicing easier. At the Munich Airport visitors’ hill (Besucherhügel) or the Zeppelinheim viewing platform you can follow the radio and the action on the runway side by side.

English, German and accents

In scheduled traffic, English is the language of the radio, and standard phrases are the lowest common denominator. That does not mean everyone sounds the same: accents, speaking speed and local quirks make the radio at each airport a little different. Native speakers do not automatically have an advantage either – anyone who speaks too fast or throws in slang makes communication harder.

In Germany, German is also permitted at many airfields in visual flight traffic, with its own German standard phrases. When which language applies and which radiotelephony licenses exist is explained in the post English or German on aviation radio. If you want to get to know the radio from the other perspective, the article Becoming an air traffic controller shows the way into the profession, and the organization behind it is introduced in the post on DFS Deutsche Flugsicherung.

Conclusion

Radiotelephony phraseology is not a secret language but a deliberately small toolbox. A fixed order, unambiguous standard words, special number pronunciation and the readback of safety-relevant instructions ensure that misunderstandings stay rare. For you at the spot, this means: with a handful of phrases you know when someone is taking off, landing or going around – and you are ready with the camera in time.