person who has the tickets had a change of plans, or due to
Airline tickets can be expensive no matter how you look at
Fare comparison sites are usually the first stop for people
Why it's awesome: Norwegian Air is one of the most aggressive and controversial airlines in the world. The low-cost carrier had drawn the ire of its US competitors by proposing a plan to operate trans-Atlantic flights using an Ireland-based subsidiary. The airline's critics claim that such a move would allow Norwegian to flaunt Norway's strict labor laws and use Ireland as a flag of convenience. Norwegian has denied these accusations. Regardless, Norwegian CEO Bjørn Kjos has won US government approval to launch ultra-low-cost trans-Atlantic flights from smaller airports in the Northeastern part of the country.
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.
Keep your dates flexible. Many airlines have specific requirements for a minimum and maximum total number of days to be spent in a location in order to get the best deal. For the cheapest flights, stay for a minimum of 2 nights and a maximum of 30. Try to stay at your destination over a weekend, as flights that bookend a Saturday night are cheaper than those that lack a Saturday stay.