From Frontier Airlines in the U.S. to Ryanair in Europe and AirAsia in Asia, you’ve probably flown a low-cost airline at least once on your travels. These airlines offer low-cost fares with no extras like seat selection, bags, or drinks included with your fare. After all, that’s their business model: Get you from A to B as cheaply as possible, and charge you for every extra.Sometimes referred to as “budget airlines,” low-cost airlines often operate routes that are underserved by major airlines. For example, ...