1. Auction sites A flight auction site is a site which auctions off their available offers to the person who offers the highest price. You put in a bid as to what you are willing to pay and if your bid is accepted you will end up with the flight.
It is likely that the price you will end up with will be considerably cheaper than a conventional ticket to the same destination. However, you can only specify the destination you wish to travel to and the departure and arrival dates. Things such as preferred airline and the flight times are usually out of your control.
2. Apex tickets You can save up to 60% when you book non-flexible, non-refundable apex tickets. They must be booked and paid for well in advance of departure, varying between seven days and a month, a minimum stay abroad is required and no stopovers are allowed. Ideal for the flexible, committed traveller as there can be up to 12 different fares for the same seat in economy class.
3. Courier travel A little known way of obtaining cheap flights is by signing on as an air courier with a courier company. The courier company purchases the ticket from the airline and sells it to the courier for a really cheap price in return for their work.
Check the company is officially recognized by a trustworthy source. A good place to check is 'IAATC - International Association of Air Travel Couriers'. They have lots of information and advice on the most trusted courier companies, the best offers to various destinations and up to date information on last minute flights. Alternatively, just look up "courier companies" on the internet or in local directories.
Anyone who is over 21 can become an air courier. Check each company's conditions before signing on. After signing up as a courier you will usually be required to show up at the airport at a certain time to be given instructions as to where to meet the courier agent (the person you are handing the baggage over to at the destination airport).
Couriers can save up to 75% off the regular air fare price. Destinations are limited however and the length of stay usually varies between 14 and 21 days.
This is a good option if you are looking for a unique and interesting way to save money on your airline ticket.
4. Ticket consolidators Buy tickets through consolidators (ticket brokers) who buy blocks of tickets and sell them at a discount to help an airline fill up all available seats. Check the travel section of the newspaper or online under 'Ticket Consolidators.'
5. Promotional Flight Sales Budget airlines have free 'flights sales' (or technically $1 or 1GBP) to build up a customer base or promote their newest routes and services by slashing fares and offering free return tickets. Always check the sale price says "includes taxes or charges" though, or it can still add up to $47/30GBP each way. Keep up to date by subscribing to their newsletters.