An Extremely Rare Airplane

The Museum of Flight in Seattle has an impressive collection of aircraft.

All pictured here with information about both the type in general and their example in particular: https://www.museumofflight.org/exhibits-and-events/aircraft/

Civil and military, old and new (they have a Blackbird and a Concorde on show, to name but two). 

But the absolutely rarest gem must be this:

(image from their website, used here for non-commercial purposes)

Here's what it says on the sign:

https://www.museumofflight.org/Exhibits-and-Events/Aircraft/Wonder-Womans-Invisible-Plane

Paul V.