Not many people know about that one. The Germans during WW2 thought that switching the wing in flight for traditional to that would improve performance. Many of their concepts have tha idea in it.

this airplane type actually a copy out from the german technologies,please check back in the nazi era
airplane.most of the airplane and jet fighter we do have today actually they are copying from the same source

Like the norththrop flying wing and the arado delta wing series.