What is one function of a SIGMET report?

A SIGMET report is specifically designed to alert pilots and air traffic controllers about hazardous weather conditions that could significantly impact the safety of flight operations. This includes phenomena such as severe turbulence, thunderstorms, icing, volcanic ash, and other weather events that might pose a risk to aircraft in flight. The primary purpose of a SIGMET is to ensure that pilots are aware of potentially dangerous situations that could affect their route or operational safety, allowing them to make informed decisions about their flight paths and altitudes.

In contrast, other options focus on different aspects of aviation communication. Providing routine weather updates pertains more to METARs and TAFs, which offer regular meteorological data rather than immediate hazard alerts. Changes in flight paths are managed through different communication methods and do not specifically relate to weather hazards. Lastly, information about air traffic congestion typically falls under air traffic control operations, which involves managing and directing aircraft to maintain safe separation and efficiency; it does not concern the immediate weather impacts addressed by SIGMETs.