In aviation, blue ice is frozen sewage material that has leaked mid-flight from commercial aircraft lavatory waste systems.
[2] These incidents typically happen under airport landing paths as the mass warms sufficiently to detach from the plane during its descent.
A rare incident of falling blue ice causing damage to the roof of a home was reported on October 20, 2006, in Chino, California.
[4] Other documented incidents include: Blue ice can also be dangerous to the aircraft itself — the National Transportation Safety Board has recorded three very similar incidents where waste from lavatories caused damage to the leaking aircraft,[12][13][14] all involving Boeing 727s.
In all three cases, waste from a leaking lavatory hit one of the three engines the 727 has mounted in the rear, causing a power loss.