Crossborder flights

The form must be filled in, signed and sent per fax to the person in charge at the airport or to the competent Customs office (according to the terms of the authorisation).

A border guard checks a pilot on the airfield next to his plane.
https://www.ezv.admin.ch/content/ezv/en/home/information-individuals/declaring-goods/importation-into-switzerland/declaring-goods/crossborder-flights.html