Today I came across a fascinating letter that had a sad occasion – a bereavement – but is nevertheless an extraordinary piece of history. It is a registered letter that was carried on the first postal flight from Vaduz to St. Gallen. Captain Wirth operated the outward flight from St. Gallen to Vaduz, while the return flight on which this letter was transported was operated by Fritz Gerber. On the outward flight, 3,004 items of mail were carried, on the return flight 15,349 – a logistical masterpiece for the time.
The letter shown here was posted in Vaduz on August 31, 1930, postmarked with a “St. Gallen Luftpost” date stamp on the same day after arriving in St. Gallen and finally forwarded to Meilen on Lake Zurich, where it arrived on September 2, 1930, as evidenced by the date stamp on the back. This first postal flight on August 31, 1930 was celebrated with a flight day, a date on which the first Liechtenstein airmail stamps were also issued. The special red postmark on the letter with the text “1st postal flight Vaduz – St. Gallen August 31, 1930” testifies to participation in this first flight.

The first airmail stamps issued on August 12, 1930, designed by H.C. Kosel; halftone intaglio printing, mixed perforations available
The Liechtenstein airmail stamps issued on this day were a set of six stamps with the theme “Airplane over landscapes”, designed by C. Kosel and produced using the halftone intaglio printing process. These stamps could only be used for airmail items, and the airmail surcharge had to be paid with these special stamps.
However, the letter I found raises questions. It is franked with the 50 centime stamp from the “Landschaften und Fürstenpaar” stamp set of 1930, which was issued on August 12 of the same year. According to my calculations, however, the franking should have amounted to 55 centimes: 20 centimes for the domestic letter, 20 centimes for the registered letter and 15 centimes for the airmail. In addition, the airmail surcharge should actually have been paid with a stamp from the airmail series. So is the letter understamped or even incorrectly franked?
This remains unclear, and I hope that someone with more specialist knowledge can help me. Anyone who is knowledgeable is welcome to share their opinion via the contact form on the website. I look forward to any reply that helps to clarify this little philatelic puzzle.