Routinely flying above 40,000 feet, the gliders set a succession of records, and the study found that mountain waves, or a series of them, could reach above 45,000 feet with vertical wind speeds ...

The sailplane then drops down into the dead zone where it’s airspeed becomes equal to its groundspeed, 60 knots. It loses speed making a 180° turn and then loses more as it turns and climbs ...

The pressurized, high-altitude Perlan 2 sailplane performed a short flight Tuesday at EAA’s AirVenture in Oshkosh, Wisconsin. [Photo: Thom Patterson] Perlan 2, the record-setting, pressurized ...