At the time, it was widely thought that the 747 would be superseded in the future by supersonic transport (SST) aircraft. So Boeing designed the 747 so that it could easily be adapted to carry freight, knowing that if and when sales of the passenger version dried up, the plane could remain in production as a cargo transport. The cockpit was therfore placed on a shortened upper deck so that a nose cone loading door could be included, thus creating the 747's distinctive "bulge".