 Every year the Swiss army dynamite certain dangerous mountainsides  to remove the threat of avalanches. As the storyline called for such  an avalanche, the film production worked alongside the army in  scouting appropriate sites for filming. Having chosen one, they were  dismayed to discover that the avalanche occurred naturally before  the crew could get there to film it so the resulting one seen in the  film is a combination of stock footage, special effects, and clever  use of close