Natural hazards to airborne traffic include adverse wind conditions, lightning, poor visibility, freezing temperatures, hail, birds, volcanic ash clouds and snow weight. Runway hazards of a natural kind include flooding and icing, large animals, storm debris, snow drifts and, in arid regions, sand drifts.
Greater than sixty airplanes have been damaged by ash from various volcanic eruptions. Damage can include pitting of wind shields which causes them to look foggy. The fuselage, wings, engines, and light covers can also be damaged by ash and are very expensive for the airlines to repair. Volcanic eruption clouds cause rerouting, cancellation, and delays in flights which is also expensive for the airlines. The accumulation of ash can also load down a plane which may cause the plane to rest on its tail. Ash on runways is another problem because anytime a plane lands or takes off the ash is resuspended. Special techniques have been developed to remove ash from aircraft and runways.