The Federal Ordinance on special category aircraft (OACS 748,941) lays down the essential conditions for the safety of air navigation as follows:
Art. 16 Restrictions applicable to free balloons
It is forbidden to release free balloons:
a) if their payload is greater than 2 kg and their capacity greater than 30 m3;
b) at a distance of less than 5 km from the runways of a civil or military aerodrome, if their capacity is greater than 1 m3. Exceptional authorization in writing may be issued by the Federal Office of Civil Aviation for the above case under paragraph (a) and by the air traffic control bodies or the chief executive of the aerodrome for paragraph (b) only.
The release of other balloons and small balloons does not require authorization for the purposes of aviation safety.
The number of balloons released simultaneously may however not exceed 300, nor may balloons be attached in clusters. Furthermore, no metal objects may be attached to the balloon.
When more than 300 balloons are released, an interval of fifteen minutes shall be respected.
The request shall be made fifteen days in advance to:
Special flight office Switzerland
Flugsicherungsstrasse 1 - 5,
P.O. Box 23,
CH-8602 Wangen bei Dübendorf
+4143 931 62 36