[myknowledge]

The Germans did, during WWII with the Ju 287. Then the Soviet Union captured the Ju-287 prototypes, along with the FSW configuration design, and subsequently developed the Tsybin LL-3. Then the United States and the Soviet Union developed their own prototype aircraft with FSW configurations. Grumman X-29 Sukhoi Su-47 Berkut

[Proud_USA_Republican]

Germans were doing incredible work on plane designs in WW2. Their failures during the Battle of Britian really pushed them to design and test planes that could gain them air superiority. The recent NatGeo special, "Hitlers Stealth Fighter" was probably one of the best programs like it I had seen in some time. The Horten 229 was light years ahead of anything the British or Americans were testing in regards to a jet engine based flying wing design.

Northrop-Grumman tested the design in 2008 and its radar cross section was only 40% compared to conventional planes. They were already testing these planes with successful flights near the end of WW2 and had planned a bomber version (Amerika Bomber) as well that could of potentially reached the eastern united states droping atomic weapons.