*4.4. Infrastructure Cost Estimation*

Most of the building and operating costs of a vertiport are unclear as long as we do not know the demand and the VTOL aircraft's performance. Besides that, who is going to pay for it? A vertiport's cost heavily depends on what VTOL aircraft design and UAM "airline" needs to be accommodated, which VTOL aircraft fleet is being operated, what demand densities need to be served and where the vertiport is specifically located.

Considering all-electric and hybrid-electric propulsion systems, ref. [101] estimated energy operating costs as well as total cost per vertiport. Assuming a VTOL vehicle power level of 200 kW required in both propulsion systems, a vertiport network of five vertiports and 500 vehicles each, will require a total cost investment per vertiport of \$72 million for operating only fully electric vehicles. This is assumed to decrease significantly to \$2.25 million if purely refueling is needed. On the one hand, the amount of required chargers (160) will impose a significant burden on the city's electricity grid, but on the other hand, a fuel-based propulsion system will face non-revenue flights if refueling operations are centralized at a specific vertiport location. However, decoupling UAM transportation services from refueling operations would reduce a vertiport's footprint, creates faster turnarounds and therefore may increase potential throughput.

For a vertiport which offers only a multi-function single pad featuring the dimension of 39 by 69 m, the estimated costs are declared to be approx. \$350,000 according to [126]. This increases to \$750,000 and \$950,000 if two or three additional parking areas are attached to the single FATO, respectively. The required footprint results into 72 by 99 m. Extending a vertiport to a linear design with one landing pad, one take-off pad and two disembarking, maintenance and embarking pads each, results into an expected vertiport cost of \$1,600,000 and a footprint of 69 by 168. For the smallest configuration of *Lilium's* vertiports being ground-based with small terminal areas and a limited set of charging stands, an initial investment of €1–2 million is predicted [125]. Elevated vertiports with larger footprints and capabilities require investments between €7–15 millions depending on the resulting size and location [125].
