Heavy air transports like the Hephaestus can carry larger units, including Commanders. They are the cheapest way to move slow and heavy units, but are relatively slow for an air unit, and don't have much armor compared to the Skyhook.

Hephaestus can also lift certain defensive structures—Guards, Twin Guards, Thistles, and Radar Towers—allowing deployment of defenses without a constructor on-site. This can be useful for rapidly reinforcing a position, or even using them offensively.