An engineless glider could soon soar above the lofty heights reached by the legendary U-2 and the SR-71 spyplanes. But first it needs to do a few test flights. On Wednesday, for the first time, the aviation nonprofit Perlan Project will fly their glider, the Perlan 2. The test flight comes in preparation for an eventual flight at 90,000 feet above the Earth, where the air is thin and its influence on the weather below is little-studied.

In order to fly, an airplane usually needs, well, air to fly through. The glider, built by volunteers and supported by aviation companies including Airbus, will instead fly through rarefied air. Only a few aircraft have ever flown so high, and most of the ones that did were rocket-powered. In balloons, humans like Felix Baumgartner have ridden that far and higher before plummeting to Earth. The current world record for glider altitude is just 50,721 feet.