* Short-haul flights, which often compete with cars and trains. Those could be plausibly served by electric VTOLs. If the claims about noise levels are true, the terminal does not need to be much larger than a city block.
* Medium-haul flights, like discussed here. The aircraft need to be much faster than the VTOLs proposed so far. Conventional runways seem to be necessary for efficiency, but they could be shorter than today.
* Long-haul flights that need big planes and long runways.
Airports that need runways are problematic, because the economic value they provide is low. There are often other more valuable uses for the land. In big and even not-so-big cities, airports tend to move away from the city over time.
For example, Helsinki recently closed the Malmi general aviation airport, which was conveniently located ~10 km from the city center. The area surrounding the former airport is now being developed as a medium-density residential area for 25k people. The runways were not long enough for current regional aircraft, and the facilities and the transit connections could not handle a meaningful number of passengers. As the alternate use as a residential area was worth billions, the airport could no longer be justified.
* Short-haul flights, which often compete with cars and trains. Those could be plausibly served by electric VTOLs. If the claims about noise levels are true, the terminal does not need to be much larger than a city block.
* Medium-haul flights, like discussed here. The aircraft need to be much faster than the VTOLs proposed so far. Conventional runways seem to be necessary for efficiency, but they could be shorter than today.
* Long-haul flights that need big planes and long runways.
Airports that need runways are problematic, because the economic value they provide is low. There are often other more valuable uses for the land. In big and even not-so-big cities, airports tend to move away from the city over time.
For example, Helsinki recently closed the Malmi general aviation airport, which was conveniently located ~10 km from the city center. The area surrounding the former airport is now being developed as a medium-density residential area for 25k people. The runways were not long enough for current regional aircraft, and the facilities and the transit connections could not handle a meaningful number of passengers. As the alternate use as a residential area was worth billions, the airport could no longer be justified.