Two 14-year-old boys and a pilot have been killed in an air accident at a Swiss summer camp, police have said.
A 17-year-old girl also sustained serious injuries in the crash, which took place in the canton of Graubunden, near the Italian border, just before 09:30 local time (07:30 GMT).
They had been attending a week-long camp organised by the Swiss Aero Club.
The club's Yves Burkhardt told reporters the flight should have been the "highlight" of the week.
"My world has collapsed," he said.
The single-engine plane - identified as a Piper PA28 - had already made one trip before taking the group up, police spokesman Roman Ruegg told news agency AFP.
The crash, which took place about 10 minutes after take off, was witnessed by some tourists who had taken an airlift up the mountain, in the Diavolezza region, he added.
An investigation has been launched, while Swiss Civil Aviation has closed the airspace in the area.
The camp, which has been running for 35 years, introduces young people to the world of flight. This year, 192 teenagers, aged 14 to 16, attended, according to local media.