Early signs of an avalanche can be hard to notice, seemingly slow and quiet. It's only as the sliding snow and ice accelerate and plumes kick up that the danger becomes obvious, but by then it's too late. The wave front generally reaches speeds much faster than most skiers can outrun and often is far wider than quick-thinking skiers can evade. Even flyers—and flying machines—could be caught by snow and rocks, falling or flung, and clouds of displaced air and powder.