Travel 11 things you need to know about flying discount airlines Spirit, Frontier and Allegiant October 19, 2018May 14, 2019 Dawn Gilbertson, USA TODAY Comments Off on 11 things you need to know about flying discount airlines Spirit, Frontier and Allegiant Spirit, Frontier and Allegiant charge for carry-on bags, don't offer free advance seat assignments and make you buy your own soft drinks.