SINGAPORE — Among displays of defense jets, passenger airliners and high-tech aviation equipment at the Singapore Airshow were electric air transport vehicles — touted as the future of urban transportation. Electric vertical take-off and landing vehicles, or eVTOLs, which can land and take off vertically can be used as air taxis, for cargo delivery, medical and emergency response transportation and as private vehicles. CNBC spoke to three of the biggest names backing eVTOLs at the airshow — Hyundai Motor Group-owned Supernal, Boeing -backed Wisk and Embraer -owned Eve Air Mobility, which seek to commercialize their vehicles by the end of...