Summer is nearly here, and for many, that means it's time to start finalizing vacation plans. The good news is that summer air travel doesn't have to cost a fortune. In fact, according to travel search site Skyscanner, there are many popular national and international destinations where the average round-trip ticket price dips this summer, in some cases by as much as 28% versus their average yearly price. Skyscanner's list also highlights a shift that appears to be taking place among travelers, away from tried-and-true destinations to less well-known options. Here are this summer's cheapest U.S. destinations, based on Skyscanner's analysis of flight booking data. All prices are for one round-trip economy ticket.