Disaster covers are the physical evidence of mail service that has been disrupted by a natural or man-made event. The scale of the disaster is measured by how much retrievable mail exists to be forwarded to the addressee. It is a unique collecting area because surviving mail is often rare.
Natural disasters—avalanches, earthquakes, fires, floods, hurricanes, icebergs, lightening, tornadoes, tsunamis and volcanic eruptions, for instance—can interact with any or the entire postal operation infrastructure. Collection boxes, post offices, processing centers, and especially transportation can all be damaged or destroyed, as was the case with the Titanic and the Hindenburg. Man-made disasters can be benign—mechanical failures of airplane engines, for instance—or malevolent. Deliberate bombings, arson, and acid are some examples of malevolent, man-made disasters.
This class of covers typically bears a Post Office handstamp or printed label or is encased in a sleeve that explains the mail's delay and damage.