Engineer: Semiplaning monohulls are a new kind of ship that can attain twice the speed of conventional ships  Due to increased fuel needs, transportation will be much more expensive on semiplaning monohulls than on conventional ships  Similarly, travel on jet airplanes was more expensive than travel on other planes at first, but jet airplanes still attracted enough passengers to be profitable, because they offered greater speed and reliability  Semiplaning monohulls offer the same advantages over traditional ships
Thus they will probably be profitable as well
It serves as one of two analogies drawn between semiplaning monohulls and jet airplanes, which function together to support the argument's main conclusion.