It must also be borne in mind that many decades must pass before such craft actually become available, and a great deal can happen in other fields of transport during this time.
Mayihlale ezingqondweni kwakhona into yokuba iinkulungwane ezininzi mazidlule phambi kokuba ezi nqanawa zokuhamba emanzini zibe khona, kwaye isigqibo singenzeka kwamanye amaziko ezothutho ngeli xesha.