In aviation, blue ice refers to frozen sewage material that leaks from commercial aircraft lavatory waste systems during flight. This substance is a mix of human waste and liquid disinfectant, which freezes at high altitudes. The term “blue ice” comes from the distinctive blue color of the disinfectant used. Airlines are prohibited from dumping their waste tanks while airborne, and pilots do not have a way to release this waste mid-flight. However, leaks can sometimes occur from a plane’s septic tank.
While rare, incidents of blue ice detaching from aircraft can happen, particularly as the mass warms during descent. This poses a risk to people and property on the ground. Between 1979 and 2003, there were 27 documented cases of blue ice impacts in the USA alone. Additionally, blue ice has historically been known to cause damage to aircraft in flight, especially to rear-mounted engines like those found on the Boeing 727. Understanding these risks is essential for both aviation professionals and the public.
