AIRMET

Definition

An AIRMET is a weather advisory issued to inform pilots of moderate or potentially hazardous weather conditions that may affect the safety of flight — particularly for light aircraft and VFR operations. AIRMETs cover less severe conditions than SIGMETs, but they are still operationally significant.

AIRMETs are especially useful for general aviation, training flights, and low-level VFR traffic.

Purpose

Warn pilots of weather conditions that may impact flight safety
Support decision-making during flight planning and in-flight updates
Assist ATC and FIS in advising aircraft operating in affected areas
Complement SIGMETs, which cover more severe phenomena

Typical AIRMET Conditions

Condition	Description
Moderate turbulence	Below SIGMET levels, often due to wind shear or terrain
Moderate icing	Affecting aircraft without anti-ice protection
Widespread mountain obscuration	Clouds, fog, or snow limiting visibility
Surface winds > 30 kt	Risk to light aircraft during takeoff/landing
Widespread low visibility or ceilings	Below VFR minima in large regions
Thunderstorms in isolated areas	Not meeting SIGMET severity

AIRMET Structure

AIRMETs are usually structured similarly to SIGMETs but may vary by national meteorological authority. A typical AIRMET includes:

Issuing center and region (FIR)
Valid time period (usually 4–6 hours)
Description of weather phenomenon
Altitude/flight level range
Area of coverage
Intensity and trend (e.g., intensifying, weakening)

Example:
AIRMET SIERRA VALID 081000/081400 FOR AUSTRIA FIR MTN OBSC DUE TO CLDS AND FOG TOPS FL080 MOV E 25KT

Translation:

AIRMET SIERRA (mountain obscuration)
Valid from 10:00 to 14:00 UTC
For Austria FIR
Mountain obscuration due to clouds and fog
Cloud tops up to FL080
Weather moving east at 25 knots

Types of AIRMETs (ICAO naming system)

Type	Code	Condition
SIERRA	S	Mountain obscuration, IFR conditions
TANGO	T	Moderate turbulence, strong surface winds
ZULU	Z	Moderate icing conditions

AIRMET vs. SIGMET

Feature	AIRMET	SIGMET
Severity	Moderate	Severe or extreme
Audience	VFR, GA pilots	All aircraft
Frequency	Regularly issued, updated	Event-driven
Examples	Moderate icing/turbulence	Volcanic ash, embedded TS, severe icing

How to Access AIRMETs

Preflight briefing systems
National meteorological service websites (e.g., Austro Control, DWD)
AIP and NOTAM briefings
VOLMET and ATIS (select advisories)
Flight Information Services (FIS) enroute

Phraseology Examples

“AIRMET in effect for widespread fog below 1000 feet, advise if deviating”
“Wien Information, OE-XYZ, request update on icing AIRMET in Salzburg sector”

Pilot Tips

✅ Always check AIRMETs during preflight planning, especially for VFR
✅ Be cautious when flying near mountainous terrain or in winter weather
✅ Use LearnATC to practice diversion decisions and weather avoidance based on AIRMETs
✅ If conditions worsen, be ready to request IFR clearance or alternate routing