During the SABER and MLS era, extensive studies of planetary wave-tide interactions in the mesosphere and lower thermosphere (MLT) have demonstrated that these processes act as an amplifying mechanism that vertically couples the MLT and ionosphere responses to sudden stratospheric warmings (SSWs). However, the role of gravity waves (GWs) in transmitting the planetary wave periodicities into the ionosphere has been long underrepresented due to limitations in both observations and models, despite the fact that gravity waves can be directly modulated by planetary-scale waves and thereby carry their periodicities while propagating upward. This talk revisits this long-standing question by explicitly focusing on the role of GW modulation and wave-wave interactions in the atmosphere-ionosphere (A-I) vertical coupling during SSWs.