Cannot be built until the Manhattan project has been completed. All units have an attack strength of 0. In addition to 40 shields building this, it also removes 1 pop from the home city. This unit is used to found new cities. Can also be used to hurry WOW building.
All terrain is crossed as if by road.
Excellent if you have a huge land mass you want to explore really quickly. Plus trade routs created using Freight produce more overall trade. More effective, and can place nuclear devices.