This clip was filmed in an ASK21 glider at Cranwell Gliding Club in England while I was sharing a set of flights with one of the club instructors (conditions were too strong for a pilot of my low experience to fly solo that day) who decided to show something interesting during his flight, which meant that I could film it. The wind was very strong especially higher up so we were able to fly above the glider's stall speed while being absolutely stationary relative to the ground below. It is a fascinating experience to effectively hover an engineless aircraft.