Formant transitions from a high front vowel to a non-high, non-front vowel mimic the formant signature of a canonical [j], resulting in the perception of an acoustic glide (Hogoboom 2020). We ask if listeners may still perceive a glide when canonical formant transitions are absent. We investigated the mapping of an Appalachian English (AE) monophthongal [aɪ] in hiatus sequences, monophthongal [aɪ.a]. If participants map this monophthongal [aɪ] to a high front position, they might perceive a glide that is not supported by the acoustic signal, which we call a phantom glide. Ninety-six participants (45 of which were native AE speakers) heard 30 different English words ending in [i], [ə], or monophthongal [aɪ] (i.e. tree, coma, pie) that had been suffixed with either [-a] or [-ja]. They were asked to identify which suffixed form they heard. Participants in both dialect groups sometimes perceived a glide that was truly absent from the speech stream. In these cases, participants mapped static formants in monophthongal [aɪ.a] stimuli to a diphthongal /aɪ/ with a high front endpoint, causing the perception of the necessary F1 fall and subsequent rise of a [j]. Using recent models of speech processing, which encode both social and acoustic representations of speech (e.g. Sumner et al. 2014), we discuss the mapping of monophthongal [aɪ] to a privileged diphthongal underlying form.