A technical problem with the air traffic control system has halted takeoffs and landings at Swiss airports, the Skyguide agency said.
“The Swiss air navigation service provider Skyguide experienced a technical malfunction in the early hours of this morning, which is why Swiss airspace has been closed to traffic for safety reasons,” Skyguide said in a statement.
“This airspace closure is in effect until further notice,” it added.
Skyguide said it was working to find a solution and would provide an update when more information was available.
A spokesperson for Zurich Airport had earlier said takeoffs and landings had stopped, while Geneva airport tweeted that traffic would not resume before 8 a.m (0600 GMT).