Due to the increase in aerial vehicle traffic, more routes in the air need to be created. But the city is getting more mega-skyscrapers and these futuristic buildings are only getting larger. And so, instead of stopping the growth of the city, why not build entryways for the aerial vehicles to travel through? This way it provides more flexibility for the city builders and planners. Then again, this might also mean a more disastrous accident where aerial vehicles might collide with others when entering the tight entryway.
