http://perlanproject.org/

Our mission is to soar up to 90,000 ft using stratospheric
mountain waves and the Polar Vortex. We will be building a special pressurized
high altitude sailplane in El Calafate, Argentina; the same location of our
record-setting flight. The flight will take place in El Calafate, Argentina and
is planned to fly in August 2013.

http://soaringcafe.com/2012/03/ssa-2012-the-perlan-project-an-interview-with-greg-cole/

The Perlan Project has one bold and ambitious mission: to soar
higher than any fixed wing manned aircraft has flown—all the way to 90,000 feet.
The flight will use atmospheric waves extending up through and beyond the
stratosphere. Such waves are produced when a high altitude jet stream that
circles the polar regions (the Polar Vortex) interacts with mountain ridge
systems.

In the Southern Hemisphere, the Argentine Andes extend to near the southern tip
of South America and are aligned north-south. During the Southern Hemisphere
winter, the high altitude winds of the southern polar vortex blow almost
perpendicular to the southern Andes, which makes Argentina the ideal location
for the Perlan Project.

A sailplane designed to fly at such extraordinary altitudes will encounter
conditions quite unlike those at lower altitudes; therefore, a completely new
aircraft design is required that takes into account the extremely low pressure
and the resulting aerodynamics and human factors.

Thanks to alex morillo.