As part of her environmental work American actress Daryl Hannah (53) was flying to Klagenfurt with Austrian entrepreneur Martin Kristek (42), to visit a solar energy facility.
The 'Blade Runner' star and her fellow passengers were shocked when a shrill alarm was triggered at 10,000m, due to a sudden drop in cabin pressure.
Oxygen masks were automatically deployed, and the plane made an emergency landing at Klagenfurt airport.
"I'm already scared enough of flying, when suddenly the oxygen masks appeared. Luckily nothing happened," Hannah told the German newspaper Bild.
It was later reported that the pressure loss was due to ice in the cabin door seal of the Cessna Citation 525 private jet.