C. Air routes connecting the East Coast to the West Coast were in place before routes that serviced the cities in the southern United States
Explanation:
The air routes were not established between all major cities across the US at the same time. The air routes started to be established in the northeastern part of the country first, and when it came to longer air routes that connected the East Coast major cities with the rest of the country, the cities that were preferred were the ones on the West Coast, not the cities on the south which were much closer. There were several reasons for this, one of which was that the East Coast cities were in better relations with the West Coast cities, and the other that it was of greater economic benefit that the two coasts are connected.
