There's still a pretty substantial employment presence in MSP for DL, but that was negotiated with the state of MN in exchange for releasing DL from the stipulation in a major loan to NW from the state that NW would retain its HQ in MSP. The headquarters, as such, is completely vacant, but some operations remain in MSP. The holding company for the wholly owned regional airlines is here, some reservations/service center, Skybonus (the corporate frequent buyer program) come immediately to mind. There's some more as well.