The Monstrons had developed time travel before their destruction. A time destroyer once pursued Iris Wildthyme's TARDIS across time. (AUDIO: The Iris Wildthyme Appreciation Society, Iris Rides Out, Midwinter Murders) Whilst Jack Harkness was working for the Time Agency, he visited the Fluren Temporal Bazaar to bid on a Monstrom time destroyer. He lost the bid to a pair of Wrightosaur mercenaries. (COMIC: Weapons of Past Destruction)