Mail on airliners
In addition to passengers, crew, luggage and hijackers, the two airliners that crashed into the World Trade Center also carried mail. Two pieces of mail are known to have survived, discovered by pedestrians on the streets of New York City. Story: "One Letter's Odyssey Helps Mend a Wound," by Pam Belluck of The New York Times, December 20, 2001, Thursday, Late Edition - Final, Section B, Page 6, Column 1.
The Hindenburg also carried mail when disaster struck on May 6, 1937. Of the 17,609 pieces of mail she carried, 358 were recovered. See <a href="http://www.slettebo.no/scout/hindenburg.htm";
http://www.slettebo.no/scout/hindenburg.htm.