New York, like all the great centres of the planet, had conurbated over a confluence of ley-lines. Running between the Adirondacks and the Appalachian Highlands, these earthly cosmic strings had fallen into disuse long before the fairies arrived. Although rich in exotic matter, a slightly altered form of the earth’s magnetic field was the only clue to their potential. However, once charged with sufficient amounts of energy the induced twist could transport small winged creatures at speeds in excess of the speed of light, without the weight gain (a most important feature).
The fairies were struck with a desire to travel. Quite naturally, they were aware of this traditional transport network (equally naturally it was something long forgotten by humans) and once the Empire State building was being struck by lightning 100 times a year they were in business.
Fairies (and friends) on the Fly in full is here