Which of the following is considered more serious, a SIGMET or an AIRMET?

A SIGMET (Significant Meteorological Information) is considered more serious than an AIRMET (Airmen's Meteorological Information) because it signifies severe weather conditions that may pose a threat to the safety of flight. SIGMETs are issued for significant weather events such as severe thunderstorms, tornadoes, turbulence, icing, and volcanic ash that can affect all aircraft. The information in SIGMETs indicates immediate hazards that pilots need to take seriously while planning their flight route and during their flight.

On the other hand, AIRMETs are used to inform pilots about potentially hazardous weather conditions but are typically characterized by less severe phenomena. They address issues such as light to moderate turbulence, icing, and widespread meteorological conditions that may not represent a significant danger but should still be considered during flight planning.

Therefore, the nature of the hazards addressed in SIGMETs is of a higher severity compared to those in AIRMETs, making SIGMETs more critical for pilots to heed.