|Degree of hazard|
|NMAC involving aircraft|
|operating under 14 CFR 121f||U||U||121||101||72||60||63||43||49||81||64||63|
a A situation where collision avoidance was due to chance, rather than an act on the part of the pilot. Less than 100 feet of
aircraft separation would be considered critical.
b An incident that would probably have resulted in a collision if no action had been taken by either pilot. Less than 500 feet would usually be required in this case.
c When direction and altitude would have made a midair collision improbable, regardless of evasive action taken.
d No determination could be made, either due to insufficient evidence or unusual circumstances.
e Incidents that are still under investigation.
f Before Mar. 20, 1997, 14 CFR 121 applied only to aircraft with more than 30 seats or a maximum payload capacity of more than 7,500 pounds. Since Mar. 20, 1997, 14 CFR 121 includes aircraft with 10 or more seats that formerly operated under 14 CFR 135. This change makes it difficult to compare pre-1997 data with more recent years' data.
KEY: R = reversed; U = data are not available.
NOTE: Includes air carriers, general aviation, military, and other aircraft involved in public-use operations.
SOURCES: U.S. Department of Transportation, Federal Aviation Administration, Aviation Safety Statistical Handbook Annual Report (Washington, DC: Annual issues). NMAC involving 121 aircraft: Ibid. Air Traffic Resource Management, personal communications, Mar. 18, 1999 and May 22, 2000.