A subspace vortex was used to transport the Xindi probe to Earth in April of 2153. (ENT: "The Expanse") Later that year, a pair of Xindi-Reptilian warships, after attacking the NX-class starship Enterprise NX-01, sped away using a subspace vortex. After observing the vortex, Captain Archer ordered T'Pol to find out what she could about it, as he didn't want the Xindi suddenly appearing without him being forewarned. (ENT: "Rajiin")