Xindi ships emerge from a subspace vortex.
A subspace vortex (also called a spatial vortex or energy portal) is an extremely fast method of transportation utilized by the Xindi. The vortices were opened by using a phase deflector pulse. (ENT: "Stratagem")
Though Gralik Durr claimed they had a range of only a few light years, (ENT: "The Shipment") vortices were actually capable of transporting a ship from the Delphic Expanse to Earth in ten hours, a voyage that would take a warp five vessel six weeks. (ENT: "Countdown", "Zero Hour") The larger a vortex is, the more unstable. Degra said he would have great difficulty creating a vortex large enough to carry the Xindi superweapon and four other vessels; he warned one or two of the ships might be destroyed. (ENT: "Azati Prime")