 Their travel speed would not have been observed from Earth as being supraluminal ⁠— neither for that matter would it appear to be so from the traveler's perspective– but the traveler would instead have experienced a length contraction of the universe in their direction of travel.And

the Earth will seem to experience much more time passing than the traveler does.So while the traveler's (ordinary) coordinate speed cannot exceed "c", their proper speed, or distance traveled from the Earth's point of reference divided by proper time, can be much greater than "c".