Flying in Bad Weather: What's Actually Dangerous?

Rain: Less Dangerous Than You Think

Rain alone is rarely dangerous to commercial aviation. Modern aircraft engines are tested to ingest water at rates far exceeding any natural precipitation. The CFM56, one of the world's most common jet engines, is certified after water ingestion tests at 35 liters per minute — roughly the equivalent of flying through a waterfall. Runways are grooved to prevent aquaplaning, and airports activate runway friction meters when rain is reported.

The real danger associated with rain is often reduced visibility or the presence of associated phenomena — wind shear, embedded thunderstorms, or runway contaminants — rather than the water itself.

Snow and Ice: Managed Through Deicing

Ice on aerodynamic surfaces reduces lift and increases drag dramatically. Even a thin layer of frost on wing surfaces — sometimes described as feeling like sandpaper — can increase stall speed by 5–10% and reduce lift by 25%. All commercial flights must be free of ice contamination at takeoff — this is a regulatory requirement, not a preference.

Ground deicing uses heated glycol-based fluids applied by specialized trucks. Type I fluid (orange) melts existing ice; Type IV fluid (green) provides holdover protection of 30–75 minutes in moderate snowfall. The "clean aircraft concept" is absolute: any doubt about contamination requires a return to the deicing pad before takeoff.

In-flight icing is managed by bleed air anti-ice systems on leading edges and engine inlets. The Boeing 787 uses electrothermal anti-ice mats on engine nacelles, avoiding the fuel-efficiency penalty of bleed air.

Fog and ILS: Precision Approaches in Zero Visibility

The Instrument Landing System (ILS) allows aircraft to land in fog with forward visibility as low as 75 meters (Category III approaches). CAT III operations require special aircraft certification, specially qualified and recency-qualified crews, and airport certification of ILS infrastructure and runway lighting. Airlines operating CAT III must demonstrate approach procedures and alternate airports in their Operations Specifications.

Most major hub airports are CAT III-certified, meaning dense fog delays rather than cancellations in most cases. Aircraft equipped with autoland systems can actually perform more precise landings in fog than manual approaches in clear weather, as the autopilot has no perception issues.

Thunderstorms: Genuine Hazards to Avoid

Cumulonimbus (Cb) clouds associated with thunderstorms are among the few weather phenomena that pilots actively avoid rather than fly through. Severe turbulence, hail, lightning, icing, and extreme updrafts can all be found in or near major storm cells. Aircraft weather radar is mandatory, and pilots are trained to route around storm cells by at least 20 nautical miles. Terminal Doppler Weather Radar (TDWR) at major airports provides real-time wind shear alerts to controllers and cockpit crews.

Wind Shear: The Takeoff and Landing Threat

Wind shear — a sudden change in wind speed or direction — is most dangerous during the low-altitude phases of flight. A sudden headwind-to-tailwind shear causes an immediate loss of airspeed and lift. The 1985 Delta 191 accident was caused by a microburst near the runway threshold. Modern aircraft are equipped with Predictive Wind Shear (PWS) systems using onboard weather radar, credited with preventing multiple subsequent accidents.

Volcanic Ash: Invisible and Engine-Destroying

Volcanic ash clouds are invisible to weather radar and can cause catastrophic engine damage within minutes. The 1982 British Airways Flight 9 incident, in which all four engines failed over Indonesia after flying through an ash cloud from Mount Galunggung (all were eventually restarted at lower altitude), led to the creation of Volcanic Ash Advisory Centers (VAACs) worldwide. Today, VAACs provide real-time ash cloud tracking, and NOTAM systems distribute ash cloud boundaries to all aircraft globally.

The Go-Around Decision

When weather conditions deteriorate below minimums, or when the approach is unstabilized for any reason, crews are trained to execute a go-around — applying full power, climbing, and flying a missed approach procedure. Despite being an entirely normal maneuver, go-arounds remain underutilized in practice. IATA's "Go-Around Decision Making" guidance, developed after several landing accidents, emphasizes that go-arounds are always the safe choice when in doubt.