Limited progress has been made at talks between Swiss Transport Minister Moritz Leuenberger and his German counterpart over flight restrictions at Zurich airport.
There was no breakthrough on Tuesday in Berlin, but both sides agreed to set up a working group and another high-level meeting in March 2007.
The contentious issue of flight paths into Switzerland's largest airport and the resulting noise pollution have poisoned bilateral relations.
In March 2003 the Swiss parliament rejected an accord with Germany, which sought to limit the number of flights permitted to use airspace over southern Germany before landing in Zurich.
In retaliation, Berlin unilaterally banned such flights to Switzerland's main hub between 9pm and 7am. This forced the airport authorities to open a controversial new flight path over affluent areas of Zurich, prompting widespread protest from residents.
On Tuesday both sides agreed to "explore new channels" to find a solution to the problem which is "seriously threatening German-Swiss relations", Leuenberger told journalists in the German capital.
"The solution should offer long-term solutions to both parties and reciprocal legal guarantees," he added.
Quality of life
For Wolfgang Tiefensee, the German transport minister, future talks should aim to find short and medium-term proposals that improve local residents' quality of life without curbing the development of Zurich airport.
"The solution should offer improvements to both sides," stressed the German minister, without disguising their ambitious objectives.
The joint working group has been given the task of preparing concrete proposals to be discussed in March, including take-off and landing options.
The actual form of any future agreement between Switzerland and Germany is still undecided, explained Leuenberger.
"Negotiations might well result in a new flight agreement, but it is not obligatory," he added.
Local opposition in Switzerland to the new flight paths is still fierce, and in southern Germany opponents of flights into Zurich airport are increasingly vocal.
Following Tuesday's meeting, the Baden-Württemberg region repeated its call to further limit flights over the Black Forest area.
swissinfo with agencies
In 1998 Germany asked Switzerland for an agreement to regulate the flight paths of Zurich-bound aircraft flying over southern Germany.
In April 2001 transport ministers from both countries agreed to limit the number of flights to 100,000 a year.
The German parliament approved the agreement in May 2002, but in March 2003 the Swiss parliament rejected the accord.
In retaliation, Berlin unilaterally banned such flights to Switzerland's main hub between 9pm and 7am and limited them to 80,000. This forced the airport authorities to open a controversial new flight path over affluent areas of Zurich, prompting widespread protest from residents.
A people's initiative in 2004 called for flight movements at Zurich airport to be restricted to 250,000. But studies predict demand to grow from 2.5 to 3.5% annually and the Zurich cantonal authorities have proposed a ceiling of 320,000 movements.
Current regulations set no limit to the number of flights and the airport has a current capacity of 350,000 per year.