Aviation Glossary
Quick reference for aviation terms and abbreviations you will see on Flight Chop.
Aviation uses many abbreviations and technical terms. This glossary covers the terms you will encounter most frequently on Flight Chop, explained in plain language.
A
AIREP
Aircraft Report. Similar to a PIREP but in a different format, often used for international flights. Contains weather observations from pilots in flight.
AIRMET
Airmen Meteorological Information. Weather advisories for conditions that may affect flight safety but are less severe than SIGMET conditions. See G-AIRMET for the graphical version.
C
CAT
Clear Air Turbulence. Turbulence that occurs in clear skies, often near jet streams at high altitudes. Called "clear air" because there are no visible clouds to indicate its presence.
Convection
Rising columns of warm air, often associated with thunderstorm development. Convective activity creates turbulence and is closely monitored by pilots and meteorologists.
CWA
Center Weather Advisory. Short-term forecasts issued by Air Route Traffic Control Centers (ARTCCs) to alert pilots of developing weather conditions. Valid for up to 2 hours.
CWSU
Center Weather Service Unit. Meteorologists stationed at Air Route Traffic Control Centers who issue CWAs and provide weather support to air traffic controllers.
F
FIR
Flight Information Region. Defined airspace boundaries used internationally for providing flight information and alerting services. International SIGMETs reference FIRs.
Flight Level
A standard way to express altitude in hundreds of feet. FL350 means 35,000 feet. Used above 18,000 feet where all aircraft set their altimeters to a standard pressure setting.
FL
Flight Level. A standard way to express altitude in hundreds of feet. FL350 means 35,000 feet. Used above 18,000 feet where all aircraft set their altimeters to a standard pressure setting.
Freezing Level
The altitude at which the temperature drops to 0°C (32°F). Important for icing forecasts since ice accumulation typically occurs near or above this altitude in clouds.
G
G-AIRMET
Graphical Airmen Meteorological Information. A graphical representation of AIRMET advisories showing areas of moderate turbulence, icing, IFR conditions, and other hazards. Updated every 6 hours with forecasts up to 12 hours ahead.
I
ICAO
International Civil Aviation Organization. A UN agency that sets international aviation standards. ICAO codes are the 4-letter identifiers for airports (e.g., KJFK for JFK Airport).
Icing
The accumulation of ice on an aircraft, typically when flying through clouds or precipitation at temperatures near or below freezing. Pilots are trained to avoid or manage icing conditions.
IFR
Instrument Flight Rules. The regulations and procedures for flying when visibility is poor or in clouds. IFR conditions mean reduced visibility requiring pilots to fly using instruments rather than visual references.
J
Jet Stream
Fast-moving rivers of air high in the atmosphere, typically between 30,000-40,000 feet. Wind speeds can exceed 100 mph. Turbulence often occurs near the edges of jet streams.
L
LLWS
Low Level Wind Shear. A rapid change in wind speed or direction at low altitudes, typically below 2,000 feet. Most relevant during takeoff and landing. Pilots are trained to recognize and respond to wind shear.
M
METAR
Meteorological Aerodrome Report. Hourly weather observations from airports including temperature, wind, visibility, clouds, and precipitation. The standard format for surface weather reports worldwide.
Mountain Obscuration
When mountains or high terrain are hidden from view by clouds, fog, or other weather conditions. A hazard because pilots cannot visually see and avoid terrain.
Mountain Wave
Turbulence created when wind flows over mountains and creates wave-like oscillations on the downwind side. Similar to water flowing over rocks in a stream. Can cause moderate to severe turbulence.
P
PIREP
Pilot Report. A report of actual weather conditions encountered by a pilot in flight. PIREPs are valuable because they represent real conditions rather than forecasts. Urgent PIREPs indicate significant hazards.
S
SIGMET
Significant Meteorological Information. Advisories issued for severe weather hazards that affect all aircraft, including severe turbulence, severe icing, volcanic ash, and widespread thunderstorms.
T
TAF
Terminal Aerodrome Forecast. A weather forecast for the area within 5 miles of an airport, covering the next 24-30 hours. Includes expected conditions for wind, visibility, clouds, and precipitation.
Turbulence
Irregular motion of the air causing the aircraft to bump or shake. Caused by various factors including wind shear, convection, jet streams, and terrain. Ranges from light (minor bumps) to extreme (very rare).
U
UTC
Coordinated Universal Time. The global time standard used in aviation. Also known as Zulu time (Z). All aviation weather reports and forecasts use UTC to avoid confusion across time zones.
V
VFR
Visual Flight Rules. The regulations for flying when visibility is good and pilots can see and avoid obstacles, traffic, and terrain. Opposite of IFR conditions.
Volcanic Ash
Fine particles ejected by volcanic eruptions. Extremely hazardous to aircraft as it can damage engines and reduce visibility. SIGMETs are issued whenever volcanic ash is detected in the atmosphere.