The fact that many airlines cover the same routes – often departing at more or less the same time, especially for long-haul, overnight flights – also has an impact on pricing. If one carrier changes price or reduces capacity, others are likely to respond by cutting or raising their fares.  Cheapair.com said fares on a particular flight will generally increase as the flight becomes more heavily booked but at certain points, fares may fall dramatically if a fare sale is launched or an airline determines that booking levels are below where they should be for a given departure date.  A good way to monitor prices without spending all day glued to your computer screen is to sign up for alerts from comparison websites such as Kayak.co.uk or Skyscanner.net. They will notify you via email when prices change.  Kayak.co.uk also has a price forecast tool that predicts whether the price of a specific flight is likely to rise or fall within the next seven days. This can be a good guide if you are unsure whether to book at today's price.  Securing a last-minute bargain is much easier if you are flexible with your departure and return dates, and if you aren't fussy about which airline you fly with. There are no guarantees that prices will fall in the weeks leading up to a flight – but when they do, the savings can be substantial.  Carolyn Monchouguy (pictured), 30, is a public relations manager who lives in London. She decided to fly home to Australia for Christmas this year and started looking for flights in September.  Ms Monchouguy wanted to fly from London to Perth between December 10 and 13 and return between January 1 and 4. She searched on comparison websites and found the prices were much higher than she expected.  "When I started looking, all the available flights for my dates were between £1,200 and £1,400 return," she said. "I signed up for daily alerts on a couple of comparison websites and noticed the prices kept going up and up – eventually the flights all cost over £2,000. I think that's a ridiculous amount to pay, so I kept looking.  "I found one flight for £950, but it was returning on the red-eye on New Year's Eve, which obviously wasn't ideal, so I held out."  On October 31, Ms Monchouguy found return flights with Emirates for £745, leaving London on December 10 and returning on January 1.  "I booked it straight away. I don't usually leave things to the last minute and always book in advance, especially at Christmas time because you are constantly told that the earlier you book the cheaper the price will be.  "I had travel agents promising me that prices definitely would not fall in the run-up to Christmas. But a friend told me she always leaves it until the last minute to book flights to Sydney for the Christmas break and she always found cheaper deals closer to the day. I'm really pleased I held out – the difference between the cheapest and the most expensive price was over £1,200."  It is definitely worth shopping around for your airfares. Ms Monchouguy's flight, which is a code-share flight with Qantas, was priced at £1,800 on the Australian carrier's website last week. That's more than double the price Ms Monchouguy paid to book the same seat through Emirates less than a week earlier.  Some airlines such as Ryanair and Flybe, and credit card companies such as Amex, offer free return trips as an incentive to sign up for a card. To qualify, you must spend a set minimum amount which varies from card to card but can be as little as 1p. To get the free flight you simply have to spend the minimum. Make sure you pay off the balance in full, however, to avoid paying interest charges. Once you have used your free flight you can cancel the card if you don’t want to keep using it.  There is anecdotal evidence to suggest companies keep a record of your flight searches and push up prices the more you search to pressure you into buying before prices “rise” further. So if you search for a flight more than a couple of times in a week you could be targeted. To avoid this, clear your browser cookies after each search – or turn on anonymous browsing.  Some carriers and airline alliances offer air passes, which are great for round-the-world trips. They allow you to create your own itinerary and book a number of flights for a discounted rate. These are most common for travel in Europe, North and South America and south-east Asia.  Business travellers love to fly on Monday mornings and return on Thursday or Friday evenings. Avoid these times – travelling midweek is usually cheaper.  If you would prefer to book your flights through a travel agent always ask them for a better deal. Agents have a lot of flexibility around pricing and are all too aware that savvy travellers can usually get cheaper flights online. Doing your research before you visit an agent could pay off – they are often prepared to beat or match an online price that is available at the time.
Contrary to popular belief, booking airline tickets late is often cheaper. We   explain how the pricing works.