Designing Safety-critical interfaces entails proving the safety and operational usability of each component. Largely taken for granted in everyday interface design, the typographical component, through its legibility and aesthetics, weighs heavily on the ubiquitous reading task at the heart of most visualizations and interactions. In this paper, we present a research project whose goal is the creation of a new typeface to display textual information on future aircraft interfaces. After an initial task analysis leading to the definition of specific needs, requirements and design principles, the design constantly evolves from an iterative cycle of design and experimentation. We present three experiments (laboratory and cockpit) used mainly to validate initial choices and fine-tune font properties.