On this day, 75 years ago, zeppelin airship LZ-129 Hindenburg was scheduled to fly from Frankfurt to Berlin and back to Frankfurt. This Germany Flight was in connection with the May 1 (May Day) celebrations, a public holiday in Germany. But strong unfavorable crosswinds up to 10 meters per second from the north-northwest made a safe emergence from the hangar impossible. Since meteorological conditions were not predicted to change in the short term, the May Day zeppelin flight in 1937 was canceled on short notice.
Instead, the zeppelin mail intended for the May Day/Germany Flight was carried on the first part of the 1st North America Flight 1937 and was dropped at the Cologne airfield Butzweilerhof en route to the United States. This mail was marked with a boxed advisory cachet.
This and many more fascinating stories about the LZ-129 Hindenburg Germany/May Day Flight and 1st North America Flight 1937 can be found in the new reference book on LZ-129 Hindenburg zeppelin crash mail: http://www.ezep.de/books/hindenburgcrash.html