Germany has stepped up pressure for flight concessions from Switzerland by tearing up an agreement governing flights from Zurich airport. The move comes after complaints from German towns lying on the flight path.
Germany unilaterally terminated the accord, which regulates in and outgoing flights from Zurich's Kloten airport.
The German transport minister, Reinhard Klimmt, has given one year's notice for the cancellation of the 1984 agreement, carrying out a threat he made in April.
Klimmt had said he would terminate the accord unless Switzerland agreed to cut the number of flights over southern Germany. Towns lying in the flight path want aircraft numbers to be reduced from 140,000 per year to 80,000.
The Swiss transport ministry said it regretted Germany's decision, but said it was confident a new agreement could be negotiated before the old one expired.
A boom in air traffic led both sides to start negotiations on revising the accord in 1998, but despite five rounds of talks, no agreement has been reached. A sixth round of talks is scheduled to take place on Friday.
The accord regulates the procedures to be used by aircraft approaching or leaving Kloten airport using German airspace. It lays down minimum altitudes at which the aircraft must fly, and bans flights along the path between 2200 and 0600.
swissinfo with agencies