Whether you may use an uncleared aircraft in Switzerland depends especially on whether you are resident in Switzerland or abroad and on the purpose for which you are using the aircraft.
Swiss residents
In principle, you may not use an uncleared aircraft in Switzerland. This also applies to rented or borrowed aircraft. A special arrangement is possible under certain conditions for 12 outbound and inbound cross-border flights per year.
You may use the uncleared aircraft for 12 outbound and inbound cross-border flights per year. The aircraft may remain in Switzerland for no more than three days.
It must land at a customs airfield (categories A to C).
You need to have each border crossing confirmed at the customs office.
These provisions also apply to aircraft rented abroad or lent by relatives, acquaintances or a flying club abroad.
Commercial use refers to the carriage of passengers in return for consideration or the commercial carriage of goods with or without consideration. The amount of the consideration is not a defining factor; payment in kind also constitutes consideration.
You may use the uncleared aircraft for 12 outbound and inbound cross-border flights per year. The aircraft must be re-exported at the end of each journey. Inland transport (cabotage) is prohibited.
The aircraft must land at a customs airfield (categories A to C).
Commercial use refers to the carriage of passengers in return for consideration or the commercial carriage of goods with or without consideration. The amount of the consideration is not a defining factor; payment in kind also constitutes consideration.
You may use the uncleared aircraft without any customs formalities, but solely for cross-border flights. This requires the aircraft to be re-exported at the end of each journey. Inland transport (cabotage) is prohibited.
In principle, cross-border flights are permitted to land exclusively at a customs airfield (categories A to C).
Exceptions exist for some category D airfields. Please contact the operator of the airfield in question to find out whether commercial flights are authorised.
Infringements
If you use an aircraft in Switzerland without authorisation or if you fail to comply with formalities, you must pay the import taxes and duties for the aircraft (customs duty, value added tax) retroactively. In addition, you can expect criminal customs proceedings to be initiated.