The SAirGroup, the parent company of Swissair and Crossair, says Zurich airport's international status could be threatened if Switzerland gives in to German demands for tighter aircraft noise controls.
It was reacting to Germany's announcement on Tuesday that, at the end of May 2001, it would withdraw from an agreement with Switzerland which regulates inward and outward bound flights from Zurich's Kloten airport.
In a statement, the SAirGroup said, "Zurich airport is Swissair's home base and also a major operations centre for the regional airline, Crossair. The demands from Germany in relation to this agreement are restrictive to the point that Zurich would lose its standing as an international hub if they were met."
On Tuesday the German transport minister, Reinhard Klimmt, said he would terminate the 1984 accord unless Switzerland agreed to cut the number of flights over southern Germany. The move came after complaints from German towns lying on the flight path. They want aircaft numbers to be reduced from 140,000 per year to 80,000.
The SAirGroup said the German transport ministry's demands would make it impossible to keep the number of flights at their current operating levels. It also said that due to the airport's proximity to the German border, a certain number of flights had to fly over areas of Germany when coming in to land.
The accord lays down minimum altitudes at which aircraft must fly, and bans flights along the path between 10pm and 6am.
The Swiss transport ministry said on Tuesday that it regretted Germany's decision, but it remained confident that a new agreement could be hammered out 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.
swissinfo with agencies