Thomas Cook actually shut their STN crew base I believe end of Summer 2017. Since then they've been using wholly third party operators, with 2x aircraft from Smartlynx, as a summer only operation.
They bring in a third aircraft to support the summer peak but this is only a temporary relocation from the Glasgow base.
For Summer 2020 it looks to reduce to just a single A320 from Smartlynx all season, only flying around six or seven routes.