Beefy bodyguards guided [Michael Klein] into the dimmed cabin of his midnight blue Agusta A119 Koala. Within moments, it lifted off, joining other airborne limousines darting over the hazy skyline. Klein is one of hundreds of new helicopter commuters in Sao Paulo, the world's fourth-largest metropolis, where the rich and powerful soar high above exploding urban ills.

En route to his mansion in Alphaville -- a walled city where the privileged live behind electrified fences patrolled by a private army of 1,100 -- Klein quietly stared out the window. His pilot clipped low over the honeycomb-like slums and clogged highways below. More than halfway through a nine-minute commute, the copter grazed over a cluster of inner-city prisons. A squad of machine-gun- toting guards stood near a perimeter wall, their gaunt faces squinting upward as Klein's copter buzzed by.

Many of the wealthy have responded by moving into guarded, walled communities such as Alphaville. Only 7 1/2 miles from the city center, Alphaville is home to 30,000 of Sao Paulo's most privileged residents. It has three helipads and four entrances and exits, all monitored 24 hours a day.