In How to find cheap flights – Part 1, I discussed how to save money on your international flights.
If you’re travelling within a region like Europe, the United States, or Southeast Asia, you should consider discount airlines as an alternative to the main airlines, or to long train or bus rides. Discount airlines (also called Low Cost Carriers or LCCs) are no-frill airlines that offer very cheap fares for “basic” service, but try to make up some of the money by charging you for every little extra: baggage check, seat selection, blanket and pillow, food, drinks, insurance, even credit card processing fee. Resist the temptation to buy too many “extras”, and these flights can save you tons of money. To get the lowest fares, book several months in advance. Fares also rise during holidays.
Not all aggregator sites include discount airlines in their search results, so you may have to use the airlines’ individual websites. One aggregator that includes several of them is Skyscanner.
Europe
In Europe, the largest and most-established discount airlines are Ryanair, EasyJet, Germanwings, and Air Berlin, but there are many others. You will sometimes see fares that appear impossibly cheap (such as 15£ or the like) but keep in mind that these are the fares without the tax, which can be as much as the regular flight price.
Norwegian, with a hub in Oslo, offers cheap flights within Scandinavia and to other European countries, as well as well-priced flights from main US cities to Europe.
Vueling, with a hub in Barcelona, is useful when flying from Spain to somewhere else in Europe. I used them to go from Málaga to Athens, but experienced a two-hour delay in Barcelona due to the late arrival of the incoming plane. I am not sure if this was typical or just a fluke. Give yourself plenty of time to connect!
Here is a very good article on the topic of budget airlines in Europe: Budget flying within Europe.

Flying over Spain on Vueling
Southeast Asia
In Southeast Asia, the discount carrier of choice is Air Asia. Their main hub is in Kuala Lumpur (with a secondary hub in Bangkok) but they have a lot of routes reaching into China and even Australia. They’re the best deal out there, with good service and few delays. Try to book at least two weeks in advance, preferably three or four. They are very convenient if you want to see several countries and want to avoid crossing land borders.
I remember paying around $50 US for an Air Asia flight between Bangkok and Yangon (Burma). This included a meal and the credit card processing fee, but not the checked luggage fee, which tends to be hefty. Here is one more reason—if you need one—to travel with carry-on only!

Bangkok, one of the hubs of Air Asia
Other pan-pacific discount airlines are Jetstar and Tiger Airways. For domestic flights within individual countries, consider Nok Air (Thailand), Cebu Pacific Air (Philippines), Lion Air (Indonesia), and Firefly (Malaysia).
If you’re travelling to Australia, you may want to try finding a good deal to Southeast Asia, and from there a cheap flight to Australia on Air Asia or another low-cost carrier. It is worth comparing the prices from this method to just searching for a straight fare from your original city to Australia.
Latin America
There are no true discount airlines operating all over Latin America. Mexico, Brazil and Colombia are the only three countries that have discount airlines operating domestically. For Mexico they are: Volaris (also flying to the US), Interjet, and VivaAerobus. Brazil has Gol (also flying to Buenos Aires and Montevideo) and Azul. Finally, Colombia runs VivaColombia.
Although not a LCC per se, Sky Airline is a Chilean airline that operates domestic flights in Chile (cheaper than LAN) as well as to main cities in Colombia and Peru, in addition to La Paz (Bolivia), Sao Paulo (Brazil) and Buenos Aires (Argentina).

Sky Airline is based in Santiago, Chile, and is the main competitor to LAN
If you are planning to fly between several countries in South America, you may want to investigate air passes instead. Those are available from One World alliance, LAN, TAM, and if you’re mostly interested in the southern countries (Argentina, Chile, Uruguay): Aerolinas Argentinas. These passes come with various conditions attached but normally require that your international ticket to South America be with them or one of their partners.
North America
Domestic flights with the United States are pretty cheap, especially with discount airlines such as Spirit Airlines, JetBlue, and Southwest (which offers low fares yet lets you check two bags for free!)
Canada also has discount airlines such as WestJet and Sunwings. Porter, although it does not market itself as a LLC, often has sales of 40-60% off (the price of the flight, not the tax portion), with the best deals reserved for people on their mailing list. Air Canada, the Canadian flagship airline, recently got in the game by introducing Rouge, its budget airline subsidiary. I flew it to Cancun earlier this year. Nothing special to report, except that you have to pay extra for every checked bag.

Porter is headquartered at the Toronto City Airport on the Toronto Islands
Flying from Canada to the USA, no matter the distance or the airline, often incurs a heavy premium. Flying from a nearby American airport instead (such as Buffalo if you live in Toronto) will sometimes drastically reduce your fare. (I just did a quick search on Kayak for a return trip Toronto–Charlotte, NC, from June 10 to 17. I got $240 CAD from Buffalo versus $459 CAD from Toronto!)
Please note that the list of discount airlines mentioned in this post is by no mean exhaustive. In addition, discount airlines are in a state of flux. New ones appear; old ones disappear. Make sure you subscribe to the mailing list of all the discount airlines you’re interested in, to receive their promotions and special offers. And remember to pack light and bring some snacks!
at 1:35 AM
You’re very right! Those who are looking to save money fromtheir flights should ensure to subscribe to the mailing list of the airlines ans also travel agencies discount promotions to receive updates and special offers. That’s what I also do.
at 5:50 PM
Everybody knows that you need to be flexible when you’re looking for cheap flights. But when it comes to last minute flights, there’s more to being flexible than choosing anti-social flight times. It also means being flexible about your destination, and the airport you’re flying from. You could find yourself in a gorgeous city that you’ve never heard about before. Alternatively you can check http://www.flight-hotel.com for updated cheap deals.