“Swiss airspace is closed to traffic for security reasons after computer failure with Skyguide, the Swiss air traffic control service,” Skyguide said in a statement.

It did not give any details about the computer crash, but said it “regrets this incident and its consequences for the clients, partners and passengers of Geneva and Zurich airports and is working flat out to find a solution.”

Earlier, Geneva’s airport said in a tweet that it was grounding all of its flights until 11 am (0900 GMT) because of the computer failure.

The Swiss news agency ATS-Keystone said international flights to Switzerland were being re-routed to Milan.