### Clue: A visionary project, like the superfortress was? (6,2,3,3)
### Answer: CASTLE IN THE AIR 
 ### Explanation: Definition: A visionary project
 Cryptic defn: Reference to the B-29 Superfortress bomber that was used, among other missions, to carry out the atomic bombings of Hiroshima and Nagasaki – with its name, spelt with a lower case initial, and its usage taken literally.
Answer: A daydream, quite unlike the plane.