Our nation and the planet face daunting challenges in intra-and inter-city transportation efficiency, accessibility, safety, and reliability, and their resultant impacts on economic growth, quality of life, environmental acceptability, and standard of living. Technology-enabled transportation system innovations can comprise some of the solutions to these challenges. Attainable options for transformations in mobility might propel some of the most impactful societal advancements since the U.S. Interstate Highway System. However, a larger framework is necessary involving stakeholders, policy, regulation, infrastructure and collaborators, all aligned around a public good outcome. These transformational options are driven by technology solutions satisfying market needs affecting the speed, cost, and safety of sustainable accessibility among global communities over a wide spectrum of scales of consumer demand. NASA refers qualitatively to such a modal advancement as "On-Demand Mobility (ODM), or OnDemand Aviation (ODA)." The term encompasses thinking about air transportation between any origin-destination pair regardless of the market sizes or whether such markets could support financially viable scheduled commercial service -not unlike our daily use of automobiles and commuter vans today. The intended markets include interand intra-urban, as well as "thin haul," or markets too small or irregular to support sustainable financial performance with scheduled air carrier services. This paper frames a study sponsored by NASA Headquarters. The study proposes to answer the following question: "Is it plausible that a new form of air mobility involving new aircraft and business models can be architected so as to raise accessibility and economic connectivity through on-demand aviation, and in doing so, complement and extend the utility we take for granted in our legacy system of scheduled airlines, interstate and intra-urban highways, and rail?" This paper proposes the key elements of a strategic context and framework for the technology strategies being considered by the U.S. Government, academia and industry (and by similar EU initiatives) affecting on-demand aviation systems. In addition, the paper introduces an approach to a high fidelity quantitative characterization of thin-haul markets. Finally, we outline the prospective roles of stakeholders, collaborators, infrastructure owners and operators, regulation, policy, international activities, and emerging technologies as enablers of transformation of 21st century democratized air mobility.