As a commercial pilot with experience in various airspaces, including frequent interactions with American pilots, I've noticed a distinct difference in their radiotelephony etiquette compared to the ICAO standard phraseology. The communication style often appears more relaxed, diverging from the standardised approach and including additional 'filler' phrases.

For example, here are a couple of phrases I've recently encountered in London airspace, which differ from the ICAO norms (airline name hidden for anonymity):

  1. Observed Phrase: “London, this is Belta 3XR with you, cruising at level three five oh”
    • ICAO Standard: “London Control, Belta 3XR, Flight Level Three Five Zero”

Or the slightly more eyebrow raising:

  1. Observed Phrase: “Hey London, Belta 324, ready to go down”
    • ICAO Standard: Belta 324, request descent”

(† addressing London Control probably not required as unlikely to be the first radio contact)

These instances highlight a casual approach that differs from the ICAO standards. My intention is not to criticise American pilots but to understand the broader context:

  1. Regulatory Perspective: Are there any initiatives by the FAA and other aviation influencing authorities in the USA, to encourage American pilots to adhere more closely to ICAO standards in international airspaces?
  2. Policy and Publications: Have there been FAA circulars or other publications addressing the radiotelephony practices of American pilots?
  3. Safety Research: Are there independent studies suggesting that strict adherence to standard phraseology among pilots, including American pilots, enhances aviation safety? 1

I am keen to learn about any efforts towards standardisation and the potential impact on aviation safety, particularly regarding American pilots' practices in international contexts.

1 I find it interesting when reviewing the US Airways Flight 1549 Transcript that on a couple of occasions Sully replied quickly with standard phrasing such as “unable.”

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    $\begingroup$ Re "Observed Phrase: "... ready to go down”" -- had to laugh at this because me and my brother used to say this when we were tiny kids ready to be helped down from our hi-chairs at the table after finished eating-- who knew that we were practicing airline pilot lingo! $\endgroup$ Dec 21, 2023 at 15:36
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    $\begingroup$ US is not so compliant with ICAO, for historical reasons (ICAO originated in Europe), many terms are not standard, starting with ATC unit names (e.g. TRACON/ARTCC instead of TC/ACC), AIP GEN 1.7 lists the differences, ordered by ICAO annex (section PANS ATM Doc 4444 for phraseology differences). $\endgroup$
    – mins
    Dec 21, 2023 at 17:29
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    $\begingroup$ @mins thanks, this is what I am looking for - differences in the AIP. Though I am interested and inclined to disagree that “ICAO originated in Europe.” ICAO is a global effort led by various countries - the first convention of course being the Chicago Convention no less! The initial creation of ICAO was led by various countries, the US having a predominant role in this. $\endgroup$ Dec 21, 2023 at 20:15
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    $\begingroup$ Interesting. I didn’t realise that ICAO was seen as a European thing $\endgroup$ Dec 21, 2023 at 21:58

2 Answers 2


Short answer

ICAO ATC phraseology is not mandatory, and is implemented by States members at different degrees, due to historical reasons:

  • ICAO ATC procedures, including phraseology, are not part of the standards and recommended practices (currently 12,000 SARP in 19 annexes), but of procedures for air navigation services (currently 6 PANS documents). PANS implementation is highly recommended, but is not mandatory.

  • Being not standards, ICAO State members may not list the local implementation differences in their aeronautical publications (AIP) at section GEN 1.7. However as PANS are important procedures, States usually give a summary of these differences in the subsection “PANS / Doc 4444”.

  • ICAO Convention is built on Paris Convention, managed between 1919 and 1944 by ICAN, the International Commission for Air Navigation. This convention was first intended to agree on sovereignty and security matters in European airspace, after the war. While ICAN was supported by the US, it was actively promoted by French Clemenceau and Albert Roper. It has been at the core of air navigation in Europe since then. When ICAO Convention was signed in 1944, Europe was already compliant, while other countries, including the US, had to manage important differences, and couldn't clear all of them easily.

Details follow.

ICAO standards

Collectively known as international SARP (standards and recommended practices), ICAO standards are adopted by ICAO Council and published as annexes to the ICAO Convention. They are intended to be included in each State member law. The Convention requires to enumerate which SARP have been adjusted or excluded locally (article 38), in the AIP of the State member, at section GEN 1.7.


ICAO Council also approves other practices, and recommend them. However because such practices are either not mature enough, contain too detailed elements subject to rapid change, or have a nature not compatible with the way the Council works, these practices are not given the status of standards. Instead of being published as annexes, there are published as “ICAO documents”.

State members have no legal obligation to use the procedures detailed in “Docs”, they only need to comply with the principles included in SARP. They have no obligation to explain in AIP GEN 1.7 how the local practices differ. However they are invited to do so.


In the area of ATC, the major documents are known as PANS (procedures for air navigation services), they include (links open directly pdf files):

  • Doc 4444, PANS-ATM (traffic management), merging previous PANS-ATC and PANS-RAC.

  • Doc 8168, PANS-OPS (aircraft operations) - Volumes I, II, III.

  • Doc 9868, PANS-TRG (training).

  • Doc 9981, PANS-ADR (aerodromes).

  • Doc 10066, PANS AIM (aeronautical information management).

Annex 10: SARP and PANS mixed

PANS-ATM are introduced by Annex 10, volume 2 (Communication Procedures including those with PANS status) which use is mandatory.

Annex 10, volume 2 provides both SARP and PANS for history reasons (PANS come from older Doc 7181, Radiotelephony Procedures, now superseded). SARP describe the principles to be used for communications and provide provide some phraseology details, which status is mandatory.

PANS are added to clarify details, but they are not mandatory. They are identified by the prefix PANS and written in italic. Examples:

  • The following words and phrases shall be used in radiotelephony [...]
    CLEARED “Authorized to proceed under the conditions specified.”
    UNABLE “I cannot comply with your request, instruction, or clearance.”

  • PANS.— As the aircraft may be guarding more than one frequency, the initial call should include the distinctive channel identification “INTERPILOT”.

Publication of differences with PANS

Explaining the differences with PANS-ATM is not mandatory. From Doc 4444:

5.1 The PANS do not carry the status afforded to Standards adopted by the Council as Annexes to the Convention and, therefore, do not come within the obligation imposed by Article 38 of the Convention to notify differences in the event of non-implementation.

However State must take it into consideration because:

5.2 However, attention of States is drawn to the provision of Annex 15 related to the publication in their Aeronautical Information Publications of lists of significant differences between their procedures and the related ICAO procedures.

FAA ATM procedures are described in JO 7110.65. As ATM procedures are critical, the major differences are actually included in GEN 1.7. Examples:

Doc 4444: An arriving aircraft may be instructed to maintain its “maximum speed”, “minimum clean speed”, “minimum speed”, or a specified speed.


The U.S. uses different speed control phraseologies. Specifically, Doc 4444 uses “Maximum Speed” whereas the US uses “Maximum Forward Speed”. Doc 4444 uses “Minimum Clean Speed” whereas the US uses “Slowest Practical Speed.”



The U.S uses only “begin descent” and does not speak to “Maintain a (number) Degree Glide Path.”

Other documents related to ATC phraseology

  • Doc 9432 (manual of radiotelephony) has the same status as PANS, it is not a standard, only recommendations.

European countries and US approaches

There are different approaches regarding the implementation of ICAO Docs. Certains States are more inclined to implement them than other, in particular European countries.

The Chicago Convention (1944) is directly based on Paris Convention (1919), a convention managed by the International Commission for Air Navigation (ICAN). ICAN was active between 1919 and 1944, it transitioned to a UN agency between 1944 and 1947 (OPACI), then became ICAO.

ICAN was impulsed in Paris at the end of WWI, with the support of the US, to deal with sovereignty of airspace.

Since 1919, ICAN/ICAO have been the core of the standardization process for international air navigation in most European countries. Remote from Europe sovereignty problems and less involved in ICAN, the US standardized their practices differently. Merging with ICAO recommendations is indeed more difficult, and done when it's worth the effort required from FAA, crews, ATCOs, etc.


In the US, there is no requirement for pilots to utilize standardized phraseology in ATC communications. I think most in the industry agree that the more standardized the communication, the level of safety increases due to reduced misunderstanding. In my experience (obviously with exceptions) the professional pilots adhere to standard phraseology. As a controller, you learn to listen to clearance read backs and pick out what you need to hear, or ask for clarification from the pilot. I believe that whatever a US pilot uses in US airspace will carryover when he/she flies internationally.

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    $\begingroup$ I’m surprised by the assertion that there is no requirement for pilots to utilize standardized phraseology in ATC communications in the US. Considering the USA’s status as an ICAO member state, I would expect the US AIP to align closely with ICAO standards, particularly those outlined in Annex 10 concerning aeronautical telecommunications. Could you clarify how this apparent discrepancy between US practices and ICAO Annex 10 is addressed within the US AIP? What differences from ICAO Annex 10 are given in the AIP? $\endgroup$ Dec 21, 2023 at 17:43
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    $\begingroup$ Used to be a controller with Toronto Approach (a Nav Canada employee I presume) who would always acknowledge with "Rog". It was a kind of a trademark. Guy was extra friendly. I think, to a certain degree, the informality brightens the mood you might say. I was always careful to be really cheerful and polite with ATC ("good morning" "see ya", "have a great one" where air time permitted). I thought it made everybody's day better and fostered goodwill. I think a stricter environment isn't much safer and is just less pleasant. Granted, oddball wording is a bigger issue b/c of the confusion risk. $\endgroup$
    – John K
    Dec 21, 2023 at 22:05
  • $\begingroup$ @tedioustortoise, what Annex 10 standard is not being followed? The list of differences with ICAO standards is common for every country and is found in the GEN 1.7. faa.gov/air_traffic/publications/atpubs/aip_html/… $\endgroup$
    – Timbo
    Dec 23, 2023 at 12:23
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    $\begingroup$ @Timbo my overall point is a distinct difference in radio etiquette compared to that described in: ICAO Annex 10 Volume II Chapter 5, ICAO Doc 4444 Chapter 12 and in ICAO Doc 9432 $\endgroup$ Dec 24, 2023 at 16:15

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