Not exactly, AC expanded TANGO and has now put its fares onto almost all AC domestic and many key transborder routes and flights, and actually increased the service offering [meals and free non-booze drinks on long hauls; enhanced inflight sales menu on shorter flights. Now that AC has negotiated operating costs on mainline down to TANGO staff levels, it can do this and there is no need to keep a separate fleet or schedule. In truth, I dare say AC mainline domestic/transborder is becoming TANGO. If the majority of passengers are buying those fares, it is the others -- who are definitely in the minority -- who are now the adjunct. AC is just saving money by rationalizing their NAmerican service in this fashion. [Just as I am rationalizing the ongoing viability of TANGO for the sake of debate...]

As for DL, all new managements have the prerrogative to assess their predecessors plans and adjust them accordingly based on marketplace realities.