I was under a prior impression that the Germans pioneered swept wing design with their rocket and jet powered aircraft.
Because the XP-55 went on the drawing boards in 1939, I now have to assume swept wing design for high speed aircraft was a widely understood technology even though the Germans may have been the first to make use of it in an operational aircraft.
I like the way the plane looks. Because i never before heard of it, I did a little research and concluded that this particular article must have been run on a slow news day because performance-wise, the XP-55 was something of a dog. Even though the author calls it the "ascender", it's climb rate was one third of the P-38 and one half of the P-51's climb rate.
See also the XP-54...http://en.wikipedia.org/wiki/Vultee_XP-54
And the XP-56...http://en.wikipedia.org/wiki/Northrop_XP-56_Black_Bullet
A trio of experimental aircraft designs that the USAAF looked at as WW-II was ramping up.
Also the Fisher XP-75 while not an experimental, per se, aircraft could fall into this group as well.
http://en.wikipedia.org/wiki/Fisher_P-75_Eagle
Regards
alfa6 ;>}