Significant Meteorological Information
A weather advisory issued by Meteorological Watch Offices to warn of hazardous conditions — volcanic ash, severe turbulence, thunderstorms, sandstorms — affecting aircraft in flight.
What is SIGMET?
A SIGMET is a high-priority weather advisory issued by designated Meteorological Watch Offices (MWOs) under ICAO standards. SIGMETs cover weather phenomena that pose a significant hazard to aircraft in flight, including severe turbulence, icing, thunderstorms, sandstorms and dust storms, volcanic ash, and radioactive debris clouds. They are valid for up to four hours (six hours for volcanic ash and tropical cyclones).
There are two specialized variants: Volcanic Ash SIGMETs (issued in coordination with VAACs) and Tropical Cyclone SIGMETs. Volcanic ash SIGMETs are especially consequential for airspace risk — the 2010 Eyjafjallajokull eruption generated SIGMETs that effectively closed North Atlantic airspace for six days, stranding over 10 million passengers.
In 2024, Baghdad dust storms triggered multiple SIGMETs that closed Iraqi airspace for hours at a time, adding to the already complex risk landscape in the Middle Eastern corridor. The 2024 Reykjanes Peninsula eruption sequence in Iceland generated volcanic ash SIGMETs affecting North Atlantic routes, though improved ash dispersion modeling prevented a repeat of the 2010 mass closure.
Why It Matters for Airspace Risk
SIGMETs represent the meteorological component of airspace risk, often compounding conflict-driven disruptions. When weather hazards close additional routing options that airlines were using to avoid conflict zones, the cascading effect can be severe. FlySafe integrates SIGMET data alongside conflict zone information to provide a complete picture of airspace accessibility — because a volcanic ash cloud over a critical rerouting corridor can have the same operational impact as a FIR closure.
Key Facts
- •Standard SIGMETs are valid for up to 4 hours; volcanic ash and tropical cyclone SIGMETs are valid for up to 6 hours.
- •The 2010 Eyjafjallajokull volcanic ash SIGMETs led to 6 days of North Atlantic closure, affecting 10+ million passengers.
- •Baghdad dust storm SIGMETs in 2024 caused repeated closures of Iraqi airspace, compounding conflict-driven routing challenges.
- •Nine Volcanic Ash Advisory Centres (VAACs) coordinate with MWOs to issue volcanic ash SIGMETs globally.
Related Terms
Related Case Studies
This definition is for informational purposes. Always consult official ICAO/EASA/FAA documentation for regulatory definitions.