To see that there's only one airworthy B-29 makes me have a sad.

Since the late 60s, the most that have ever been airworthy at once was, as I recall, 5. Boeing was under-writing the complete restoration of another example ("Doc") in the 90s, but ran out of money for the project after 9-11, and progress seems to have been halted for several years now. B-29s are tremendously expensive and maintenance-intensive to remain operative (144 spark plugs must be changed annually, for example). She was grounded for corrosion, but stayed that way because they FINALLY were able to convert her to more common, later R-3350 motors. This should substantially lower operating costs and increase reliability.