In this paper, beginning with a concise overview of the Available Transfer Capability (ATC) evaluation methods, we make a proposition for reliability management in the planning horizon of deregulated power systems through the concept of Adequacy Resiliency. The derived indices are meant as indicators of adaptability of power systems to ensure the required reliability levels. Improvements to this conceptualization upon the deployment of Flexible AC Transmission System (FACTS) devices are then put forward. We also explore the option of employing the created indices to the operational horizon of power systems, explaining the means of market enhancement. Core reliability issues arising out of the usage of FACTS are then discussed.