Video via the CAF.
...the world's only airworthy Boeing B-29A Superfortress 44-62070, N529B, 'Fifi' of the Commemorative Air Force (CAF) returned to the air after a four-year grounding, and after the development of a new engine system setup.
“I am deeply pleased to see FIFI fly again after such a long wait,” said CAF General Staff member, Neils Agather. “Today’s flight is a product of the dedication of many people, Gary Austin, Dave Miller and many more volunteers. We must also thank Jim Cavanaugh for his support. My parents, Vic and Fifi, would be proud.”More from the CAF here.
For most of the post-Superfortress era, 'Fifi' has been the sole flyer, with only a couple of other airframes ever likely to be in a position to fly again at best. As the sole airworthy example of the worlds' first nuclear bomber, it is an important and historic type to have in the air.