Engineers or Space Jockeys are humanoid, hairless, and with very pale skin, through which many of their blood vessels can be seen. His eyes are said to be "seemingly dead", with pupils in the shape of oblong crosses.
Engineers stand between 9 and 12 feet tall and, like humans, breathe oxygen. However, they are apparently capable of withstanding higher carbon dioxide concentrations than humans: they can breathe unaided and unprotected on the surface of LV-223, which has carbon dioxide concentrations that would be lethal to humans.
The Engineers possess great physical strength, as demonstrated when one kills one of Peter Weyland's bodyguards by sending him flying across the room with a single blow.