The Convair X-6 was a proposed experimental aircraft that never left the drawing board. It was to have been built to investigate the practicality of powering a large aircraft (for example, a strategic bomber) with a nuclear reactor.

To provide a testbed for carrying an operational reactor in flight, a single B-36H was modified to carry one. This aircraft (first designated XB-36H, then NB-36H) did not use the reactor to provide power for propulsion, but was used to monitor its functionality. The project was cancelled after 47 flights and declassified in 1955.