Urban Air Mobility (UAM) is an emerging form of aerial transportation which plans to use electric Vertical Take-Off and Landing aircraft (eVTOLs) in urban areas. Realistic demand estimations are required to determine if demand would be sufficient to warrant implementation of UAM in urban areas. However, modelling UAM demand accurately is complex due to the infrastructure required for implementation and the lack of research available. Therefore new approaches are needed which begs the question "How can UAM demand in urban areas be estimated?". In this article, the Île-de-France region was used as an example and its demand for UAM was estimated. To perform this demand estimation, the four-step model was followed with activity-based and discrete choice models being used in trip generation and mode choice respectively. By doing this, the number of trips produced by and attracted to each zone was determined, as well as the mode of transportation individuals would utilize. Despite this model achieving a valid demand estimation, it is limited as many trips were neglected due to the use of an inter-zonal approach. It was found that the zone with the highest attraction per day is Paris, with 61.28 % of the total attraction, followed by Hauts-de-Seine (11.76 %). The key result of our model was that UAM had a mode share of 34.1% in our data set when competing with cars and public transport, hence UAM is viable in Île-de-France for inter-zonal trips. From this, a more general method that can be applied to other regions can be developed and used in the future. For future UAM demand estimation models, the main recommendation would be to use household-based approach instead of a zonal approach during trip generation, leading to the inclusion of more trips in the data set and the consideration of vertiport placement.@en