The Satellite Communications (SATCOM) industry is undergoing revolutionary changes as next generation technologies enable ubiquitous and diverse service offerings at an order of magnitude lower price point. The flexibility to roam between hybrid service providers comprised of government, commercial and international systems is an important attribute of the DoD SATCOM Enterprise that delivers high capacity, global coverage and resiliency to warfighters. Terminal flexibility to operate across networks, in multiple frequency bands, and supporting various waveforms/modems is a key capability in an architecture where roaming at the speed of military operations for assured communications is essential. What follows is the results of the Air Force Space Command (AFSPC), Space and Missile Systems Center (SMC), Advanced Concept Division (MCX) pioneered Flexible Modem Interface (FMI) effort which establishes the building blocks for a SATCOM Enterprise. FMI has been matured through a series of technology development initiatives, including a multi-vendor demonstration of the architecture, interfaces, and operational benefits of flexible terminals. The results of the rich learning through various vendor implementation of the core FMI capabilities and robust demonstrated use cases paved the way to the future FMI development.