Although it is arguably quite tough to save up enough miles to get a free flight, using the miles that you've accumulated to offset ticket prices or upgrade seats can still help you save some serious money. Taking advantage of the bonus offers you get when you sign up for top travel credit cards is definitely the easiest way to collect enough miles for 100% free flights.
Why it's awesome: Since its inception in 1998, New York-based JetBlue has helped raise the standard of service and amenities for low-cost carriers in the US. The airline's signature mood lighting, friendly service, complimentary satellite TV along with free food and snacks make it an industry leader economy flying. In fact, at 34 inches of pitch, JetBlue's Airbus A320 fleet has the roomiest economy seats in the US.
While the above search engines are great, they do not always include small airlines, especially in less popularly booked routes and/or in remote regions. If you're flying somewhere obscure, Google search and ask around if there exists a local airline. While in South America we learnt that the LADE Air in Argentina (run by the military) has cheap flights to Patagonia, which is of course not listed in mass search engines online.