Purpose - We introduce and analyze an innovative transportation system called flexible mobility on demand (FMOD). FMOD provides a menu of optimized travel options in real-time. Practical considerations related to the business model for FMOD are taken into account as a prestudy for the pilot that will be conducted in Japan. Design/methodology/approach - A modeling framework of FMOD is developed that integrates scheduling, routing, assortment optimization, and choice modeling methodologies. An assortment optimization model is developed with an objective function to maximize operator profit and consumer surplus. Findings - The FMOD system is analyzed through simulation experiments in a Japanese case study. Simulations are presented for Hino city in Tokyo with different numbers of vehicles in the fleet. This analysis provides insights about the fleet size necessary to maintain reasonable levels of operator profit and consumer surplus. Originality/value - We consider a business model for FMOD that offers flexibility to the operator in terms of who provides resources. The resources are managed with dedicated and non-dedicated services. The experiment indicates that operators can determine the size of the dedicated fleet based on an objective function that maximizes operator profit and passenger satisfaction.