[Paleo Conservative]

The first 747 prototype is loaned out to a museum now ( I wished the Smithsonian - Air&Space Museum would have gotten it).

It was used to flight test the PW and RR engines for the 777, and it has been used by Boeing for flight testing various other equipemnt.

[Central Scrutiniser]

The new Smithsonian Air and Space Annex at Dulles has the prototype 707 on display, its gone through all kinds of mods since day one, it looks great. They also have a Concorde and the only remaining Stratoliner.

Wish they had the surviving XB-70 on display, but its at Wright Patterson.