The steady headwind is all it needs to continue to create lift and therefore fly.
The determining factor here is how long the pilot can continue to fly the aircraft as it's groundspeed takes it out of visual range.
A glider in a steady headwind capable of keeping it aloft, while being controlled in a manner that prevents it from turning downwind or otherwise crashing, can stay aloft until it's receiver battery dies and that control is lost.
It's essentially a kite without a string, and kits don't need motors. They also generally don't have airfoils. All they need is angle-of-attack and a headwind and they can stay there indefinitely.
BRIEFING 3 - THE EFFECT OF WIND ON THE AIRCRAFT IN FLIGHT
There is probably more nonsense talked and written on this subject than any other connected with the practical side of flying! In reality, the matter is very simple - it is just that so many people find it hard to accept.
Provided that your flying area is clear of vertical obstructions (houses, trees, hedges, hangers etc.) the wind will blow fairly steadily from a constant direction once the aircraft is above about 50ft. Below this height, and depending on the surface of your flying site and the proximity of obstructions, there will be some turbulence both vertical and lateral.
Once you understand this principle you will see that a turn from an into wind heading to crosswind will appear to be a fairly sharp turn when seen from the ground and a turn from downwind to crosswind will appear to be slow and elongated. You must accept these visual effects for what they are and remember at all times that if you have not altered your throttle setting and the aircraft is at constant height then your airspeed is constant and the aircraft is in no danger of stalling.
Once the aircraft has climbed out of this turbulent level it is, in effect, flying in a steadily-moving block of air. Thus, with a windspeed of 10 mph the block of air in which your aircraft is flying is moving downwind at a speed of 10 mph. So, your aircraft which