The UNIFIER19 project is developing the design of an innovative airliner concept that will offer a new, sustainable and cost-efficient air mobility solution. This is intended as a keystone enabling Europe’s Flightpath 2050 vision, which envisages that virtually all EU citizens shall reach any continental destination in less than four hours, door to door, by the year 2050. A 19-passenger near-zero-emission aircraft will designed to provide a diffused service connecting smaller airports to each other (miniliner) and with hubs (microfeeder), accommodating both scheduled and on-demand shuttle flights. Exploiting the sparse, underused European small airport network, UNIFIER 19 will offer commuters a radically new mobility experience that will be as simple to use as a bus. The multi-objective interdisciplinary optimization will explore a vast design space, considering all possible combinations of aero-propulsion systems (blended wing body, distributed electric propulsion, wingtip propellers, box-wing, …) and hybrid-electric architectures (lithium batteries, internal combustion engines, fuel cells, gaseous/liquid hydrogen systems, …). A fundamental role will be played by chemical and noise emission footprint objectives, as well as appropriate production and operating cost indicators. DAER-PoliMI plays a key role in the project, deploying its expertise in conceptual and preliminary aircraft design, cost, performance and environmental impact analysis, and analysis of flight operations and procedures applied to innovative aerodynamic and propulsive configurations.