Do the terms "Airprox" and "Near mid-air collision" mean the same? If not what is the difference between them?

  • 1
    $\begingroup$ Where did you see these terms? $\endgroup$
    – Ron Beyer
    May 7, 2018 at 12:37

2 Answers 2


A Near Mid Air Collision (NMAC) is an Aircraft Proximity (AIRPROX), but an AIRPROX is not necessarily an NMAC. NMAC is used by the FAA (see 7-6-3 in the AIM), while AIRPROX is used by ICAO.

NMAC is empirically defined as coming within "100 feet vertically and 500 feet horizontally" of the other aircraft, whereas AIRPROX is categorized from A to D. The A to D categories are not empirically defined.

A - Risk of collision.
B - Safety not assured.
C - No risk of collision.
D - Risk not determined.



AIRPROX is the phraseology recommended by ICAO, midair collision, close call and near miss can also be used, but not as a standard phraseology!

  • $\begingroup$ So under ICAO recommendations, if you collide with another plane and it's somehow not a mayday scenario, you don't say anything other than that you came close? $\endgroup$
    – Someone
    Mar 31, 2023 at 2:13

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