Why is it numbers are not always pronounced in a phonetic way? For example a flight number of 2390 is pronounced "twenty-three ninety" instead of "two three niner zero"

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    $\begingroup$ I thought you were going to ask, why isn't it pronounced two-tree-niner-zero. $\endgroup$
    – J W
    Commented Mar 14, 2016 at 12:46
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    $\begingroup$ What are you basing this off of @Devron? Are you talking about actual ATC communications or announcements? $\endgroup$
    – GdD
    Commented Mar 14, 2016 at 12:50
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    $\begingroup$ From actual ATC communications from LiveATC $\endgroup$
    – Devron
    Commented Mar 14, 2016 at 12:59
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    $\begingroup$ Callsigns are only there to distinguish - there's usually no CAP20390 AND CAP2390 (which could both be twenty-tree-ninety) in the same airspace. You'll never hear this when a single wrong digit is important, like headings, frequencies etc $\endgroup$
    – Sanchises
    Commented Mar 14, 2016 at 13:08
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    $\begingroup$ @Devron That is also FAA-land specific. In ICAO-land, it would be Two Tree Niner Zero as you correctly pointed out. At least by the book... $\endgroup$ Commented Mar 14, 2016 at 13:29

1 Answer 1


The FAA's ATC orders (section 2-4-20) say that the 'group form' should be used by controllers when talking to any aircraft with an FAA authorized call sign. So you would expect to hear it with airline traffic but not private flights:

  1. Air carrier and other civil aircraft having FAA authorized call signs. State the call sign followed by the flight number in group form.

NOTE- “Group form” is the pronunciation of a series of numbers as the whole number, or pairs of numbers they represent rather than pronouncing each separate digit. The use of group form may, however, be negated by four-digit identifiers or the placement of zeros in the identifier.

EXAMPLE− “American Fifty−Two.” “Delta One Hundred.” “Eastern Metro One Ten.” “General Motors Thirty Fifteen.” “United One Zero One.” “Delta Zero One Zero.” “TWA Ten Zero Four.”

  • $\begingroup$ Followup question, then: what is the reasoning behind this ATC Order? In what way is Group Form beneficial in this instance, while being undesirable for headings, frequencies, altitudes, etc? $\endgroup$
    – Ralph J
    Commented Mar 14, 2016 at 14:37
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    $\begingroup$ Group form is much shorter to say, taking up less radio traffic. Also, the exact digits are not important, so long as the aircraft understand "he's talking about me". With frequencies, headings, altitudes, etc, the exact digits are important. $\endgroup$
    – abelenky
    Commented Mar 14, 2016 at 15:00

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