The title "Hot-Air Artist" seems to be a misnomer, as Colonel Post used hydrogen gas, not hot air, to keep his contraption afloat. However, the "hot air" may be a reference to his humbugging showman personality.
Colonel Post, speaking of the wonders of the 1920s, cites 20 story skyscrapers and cars going 40 mph. In 1920 the NYC Woolworth building was 55 stories tall and there were commercially available cars that could hit 120 mph.