Before a helicopter takes off from an airport on the Norwegian coast to fly to an offshore installation it is cleared in the usual way and is followed by the air traffic control; even after having left controlled airspace the helicopter gets flight-following and alerting services as long as contact can be kept by vhf radio.

When the helicopter approaches its destination it has to enter the platform area by flying over a certain reference point (e.g. an outer platform, Fig. 1), which is to be passed at an altitude of 500 feet and which uses a special frequency for its non-directional beacon (NDB) transmissions; it can thus be easily recognized. Before the reference point is reached, radio contact between the helicopter pilot and the platform area will have been established so that necessary information can be transferred. The pilot then asks all platforms to turn off their NDB's and his destination platform to turn on its own (all NDB's unless otherwise mentioned use the same frequency).