The second phase of an aviation deal with Germany came into force on Sunday, further restricting weekend flights to Zurich airport - Switzerland's biggest hub.
Phase two extends an existing ban on night-time flights through German airspace.
It came into effect exactly one year after the first phase of the accord, which banned aircraft en route for Zurich from crossing German airspace between 2200 and 0600.
As of Sunday, flights are now prohibited between 2000 and 0900.
The situation means less noise pollution for residents of southern Germany, but greater disruption for people living in the vicinity of Zurich, with more aircraft coming in to land from the west instead of the north.
Despite the new deal, five aircraft were allowed to cross German airspace before 0830 on Sunday, said Zurich airport spokesman, Jörn Wagenbach.
They were heavy planes and could not approach Zurich without flying over Germany, the Federal Aviation Office said.
The accord is being enforced despite strong opposition in Switzerland and the fact that neither the Swiss nor the German parliaments have ratified it.
Switzerland's national airline, Swiss, and the operators of Zurich Airport, Unique, have warned that the tougher restrictions will lead to major disruption in air traffic.
They have argued that parts of the aviation agreement contain "discriminatory measures" and that the restrictions could reduce flight capacities by between 25 and 30 per cent.
But their appeal against the flight ban extension was thrown out by a court in Baden-Württemberg - a German state bordering Switzerland - on Thursday, paving the way for the agreement to come into force.
The air transport accord is aimed at ending a long-running dispute between the two countries over noise pollution.
Residents of southern Germany have long complained about aircraft noise territory and their complaints led the German government to seek a 30 per cent reduction in the number of flights crossing German airspace en route to Zurich.
Both countries agreed to a reduction in the number of flights from 150,000 to 100,000 per year, a ban on night flights and a reduction in weekend aircraft movements.
A spokeswoman for Zurich airport said it was geared up for the change and delays had been written in to timetables.
But she said the real test of the new system was not expected to come until the first weekend of November when it would be enforced for three consecutive nights.
swissinfo with agencies
As of Sunday planes coming into land at Zurich airport will be banned from flying over Germany between 2000 and 0900.
Previously night flights were banned between 2200 and 0600.
Under the Swiss/German accord the number of flights over southern Germany is also being reduced from 150,000 to 100,000 per year.