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Glide based efficiency crafts absolutely need thick atmosphere. They don't have supersonic jets.

The U2 was subsonic. Also, un-powered gliders can get up to impressive altitudes.

> The unmanned glider, which is powered by two small propellers,

I’m confused by the article and the above comment. Isn’t a glider by definition unpowered?

Checkout [1]. Easier to say "motor glider" or "powered glider" than "powered airplane with glider like configuration".