Two Swiss army pilots were killed Wednesday when their helicopter crashed on the St Gotthard mountain pass, air force commander Aldo Schellenberg said.
A third crew member was injured in what was the second deadly Swiss air force crash since August.
The pilots had flown four French officers and Swiss military personnel to the Alpine pass as part of a bilateral inspection visit.
Shortly after the passengers had disembarked and the aircraft had taken off, it crashed.
Eye witnesses said the helicopter touched a power line before the accident, Swiss news agency sda reported.
At a press conference in Bern, air force officers said they could not confirm this and pointed to the ongoing investigation.
"We have no solid findings yet about the causes of the crash," Schellenberg said.
The commander was close to tears as he broke the news of the accidents, just weeks after a fighter jet pilot died in a crash on August 29.
"I am immensely sad that we have to mourn victims yet again," he said.