Runway hazard is a term used to describe any potential danger that could affect the safety of an aircraft while it is taking off or landing. Two common runway hazards are FOG and ICE. FOG is a cloud-like mass of tiny water droplets suspended in the air, which can reduce visibility and make it difficult for pilots to see the runway. ICE is a frozen form of water that can accumulate on the runway and cause slippery conditions, making it difficult for aircraft to take off or land safely.