Recently, I've watched Air Force One and I heard ATC and the pilots say "Acknowledged." instead of "affirm" or "affirmative" as I've learned..

Is it common to say both? Or might "Acknowledged." just throw the controller / pilot off?


5 Answers 5


"Acknowledged" means I heard you & understood what you said & I take responsibility for the information you just gave me.

"Affirm" and its opposite, "negative," are answers to a yes/no question.

They aren't really interchangeable, although Hollywood script writers are notorious for getting details like that wrong.

An example of correct usage would be, "Callsign 123, is your ride smooth at FL350?" "Callsign 123, affirm." (Answers the question, yes the ride here is smooth.") Then, "Callsign 123, we've had reports of light turbulence at your 12 o'clock and 100 miles." "Callsign 123, acknowledged." (Or, "roger" is more common, but same meaning... either way, I've received & understood the turbulence report.)

To reply "roger" or "acknowledged" to the question "is your ride smooth" is incorrect, because all you'd be saying is, I heard your question. There isn't any "yes" or "no" component to either of those replies. Likewise, to reply "affirm" to the "turbulence ahead" call is wrong because there was no question being asked there. The controller just needs to know that you heard the information so that it doesn't have to be repeated.

Interestingly, the FAA Pilot-Controller Glossary doesn't list "acknowledged" at all, but lists "acknowledge" as a directive: tell me that you heard me.

It also lists "affirmative" and not "affirm" -- that may be more used elsewhere. Also, with the quality of modern radios, the risk of the initial syllable(s) getting lost & the receiver left puzzling over "...ative" has probably diminished over time.

  • 2
    $\begingroup$ I've never heard of "Acknowledged" being standard phraseology. IMO "Roger" would be the correct word to use in the examples you mention. Do you have a source for "Acknowledged" being correct phraseology? $\endgroup$ Oct 30, 2020 at 7:06
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    $\begingroup$ @expeditedescent - no, I was responding to the OP. As I noted, "roger" is what I find to be more common, although GdD seems to think it is rare. The question was asking about the difference in meaning, so that was the main point I was trying to address, rather than FAA vs UK vs whatever else is out there that I'm not familiar with. $\endgroup$
    – Ralph J
    Oct 30, 2020 at 13:54
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    $\begingroup$ In the US at least, "roger" is the correct term from the pilot/controller glossary, but I do hear "acknowledged" from time to time in casual/colloquial use. $\endgroup$
    – nexus_2006
    Oct 30, 2020 at 16:32
  • $\begingroup$ The UK's CAP413 lists AFFIRM specifically, but similarly, lists ACKNOWLEDGE only as a controller request, and not a response $\endgroup$
    – Dan
    Nov 1, 2020 at 18:37

Movies frequently get pilot language wrong, and this is no exception.

  • Acknowledge is a command, not a response. ATC would instruct a pilot to acknowledge a transmission, and that is then acknowledged
  • Affirmative is not the correct phraseology, pilots say Affirm only for yes. Negative means no, so affirmative is not said because it could be confused with negative
  • Roger is another one movies and books often get wrong. Roger just means 'I have received your transmission'. It doesn't mean yes or no, it doesn't mean you have understood the message either. It is also rarely used
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    $\begingroup$ "Roger" dates way back to the very early days of radio when there was only Morse code sent by spark-gap transmitters. A station that received a complete message and didn't require any information to be repeated sent "R" back in the reply. When radiotelephone came along, "roger" was used, being the phonetic word for the letter R. So roger means that the complete message was received and was intelligible. If the message was received and was intelligible, I think most people would think it's reasonable to expect that the recipient also understood a plain-language (not in a secret code) message. $\endgroup$
    – rclocher3
    Oct 30, 2020 at 0:10
  • $\begingroup$ So if this were happening today we'd be saying Romeo every time we got told information. Would make a lot of old war movies seem a lot different. $\endgroup$
    – CCTO
    Oct 30, 2020 at 20:32
  • $\begingroup$ +1 - @rclocher3 It is reasonable to expect that, but CAP413 explicitly states that 'roger' means 'I have received all your transmission' (page 11) publicapps.caa.co.uk/docs/33/CAP413%20MAY16.2.pdf $\endgroup$ Oct 31, 2020 at 22:38
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    $\begingroup$ Movies frequently get domain language wrong, the problem isn't specific to piloting. $\endgroup$ Oct 31, 2020 at 22:46
  • $\begingroup$ @GdD Are you saying that, "Affirmative," is incorrect phraseology? If so you're wrong. $\endgroup$
    – RetiredATC
    Feb 17, 2023 at 19:01

In the UK, the phraseology bible is CAP 413 and that does not list the term "Acknowledged" as standard phraseology at all.

The phrase "ACKNOWLEDGE" can be used by the asker to:

Let me know that you have received and understood this message.

And is responded usually with:

Acknowledgements of information should be signified by the use of the receiving stations’ callsign or Roger callsign, and not by messages such as: ‘callsign-copy the weather’ or ‘callsign-copy the traffic’

The phrase AFIRM means


One example in CAP413 has of the use of ACKNOWLEDGE is:

BIGJET 347, I am instructed by Her Majesty’s Government that you are to hold at KTN at FL270. Acknowledge

(How very British!)

Another is:

BIGJET 347, I am informed that there may be damage to the port wing tip of your aircraft. It appears that your planned flight is liable to endanger life. Acknowledge

Which does indeed feel like it needs the pilot to positively acknowledge that they have received the message. CAP413 is not explicit on what the response should be but I suspect it would simply be along the lines of

BIGJET 347, Roger, request taxi to stand.


Good question.

The appropriate term in aviation for "Acknowledged" is the term "Roger." The only time I hear the word "Acknowledged" is on Star Trek and other tv shows or movies. As mentioned above, "Acknowledged" is not a Pilot-Controller term, although a controller might ask you to "acknowledge" something he/she has said or asked, in which case you will respond with either the answer, or say Affirmative or Negative, or in some cases, just "Roger" (plus your tailnumber).

"Roger" simply means you have received the transmission. In other words, "Roger" is an acknowledgement of a transmission.

"Wilco" is rarely used, but it means "you have received the message and will comply", some old pilots combine the two in the redundant "Roger wilco."

"Affirm" is a non-standard, but widely used, abbrevication for "Affirmative." Which simply means yes. Usually pronounced "A-firm." It is the opposite of "Negative." Personally, I hate it when people use "Affirm" on the radio, but it's widely understood and controllers generally accept it in place of "Affirmative."

Don't use "Acknowledged" in place of Affirmative or Roger in aviation communication. Better yet, don't use "Acknowledged" at all in aviation. If you mean "yes" say "Affirmative." If you want to say you've received or acknowledged a transmission say "Roger."

Likewise, don't use "Copy" or "10-4" in place of "Roger."

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    $\begingroup$ At least in the UK, and I suspect the whole of Europe, Afirm is not an abbreviation of Afirmative, it's the actual correct terminology for "Yes". $\endgroup$
    – Jamiec
    Nov 1, 2020 at 17:37
  • $\begingroup$ @Jamiec that is so interesting. Thank you for this comment. Maybe that is where it has come from. International pilots from EU flying into the US, and American pilots picking up on it. That makes it a little less annoying for me. :) $\endgroup$
    – Devil07
    Nov 1, 2020 at 18:09
  • $\begingroup$ If you have a poor reception "Afirmative" and "Negative" will sound remarcably similar for two words of opposite meaning. I always supposed that's why EASA introduced "Afirm" as standard phraseology $\endgroup$
    – Radu094
    Nov 1, 2020 at 20:19
  • $\begingroup$ @Radu094 I see your point because they have similar endings, but I was thinking the opposite. Affirmative has 4 syllables and Negative has 3 syllables, so if you are expecting one or the other, if radio communications is bad, you can distinguish them by the syllables. Throwing in a non-standard A-firm, blurs it a bit for me. Generally the more syllables the word has the better it is for poor radio reception. $\endgroup$
    – Devil07
    Nov 3, 2020 at 1:35

Both are correct. "Affirm" is not non-standard.

ICAO uses "Affirm" to mean "Yes".

However FAA uses "Affirmative" to mean "Yes".

I have not been able to find any document that addresses whether it is proper or improper for pilots to use ICAO terminology in US airspace, but US controllers use FAA terminology.

ICAO Manual of Radiotelephony: www.ealts.com/documents/ICAO%20Doc%209432%20Manual%20of%20Radiotelephony%20(4th%20ed.%202007).pdf

FAA Pilot-Controller Glossary: https://www.faa.gov/air_traffic/publications/media/pcg_basic_with_change_1_2_and_3_dtd_11-3-22.pdf


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