In high-density environments, we find that loss of separation events increase linearly with the effective flight rate. And while preflight deconfliction techniques decreased the loss of separation rates, they also decreased the effective flight rate in a region. Even at the lowest volumes, we observed losses of separation occurring at rates about four orders of magnitude more frequently than occur in today’s airspace. Therefore, to achieve safe airspace usage, regardless of separation criteria, we need to apply a greater set of tools to managing flights, just like air traffic controllers do today. Relying only on simple preflight deconfliction rules and allowing flights to operate without having to use traditional airspace structures (e.g. altitude separation, one-way routes or charted arrival procedures) simply does not provide a path to safe airspace usage.