Open this photo in gallery: The Archer 'midnight' flying taxi is exhibited at the Paris Airshow, on June 21.Michel Euler/The Associated Press Just a dot on the horizon at first, the buglike and surprisingly quiet electrically-powered craft buzzes over Paris and its traffic snarls, treating its doubtless awestruck passenger to privileged vistas of the Eiffel Tower and the city’s signature zinc-grey rooftops before landing him or her with a gentle downward hover. And thus, if all goes to plan, could a new page in aviation history be written. After years of dreamy and not always credible talk of skies filled...