The best time to book your flight is on a Tuesday, at least 8 weeks (2 months) before your intended trip; however, there are also last minute travel deals as well if you are prepared to up and go within days of booking your flight.
The days of the week that you depart and arrive on also make a big difference. Generally speaking, try to avoid leaving out and returning home on a weekend day.
The time of day can also be a factor as well. You might find that a "red-eye flight" (leaving at night and arriving in the morning - or conversely leaving at the crack of dawn and arriving at night) may give you a better fare than leaving during the middle of the day. Be flexible with your days and times if at all possible.
Unless you're booking some last minute travel deal, booking a flight less than 2 full weeks prior to departure will be the most expensive. Also, remember the "Goldilocks Rule" of air travel; don't book too early and definitely don't book to late.
(this does not constitute an endorsement for Bank of America)
Here are some other tips:
Travel Midweek
International travel deals are entirely based on availability and since most people travel over the weekend (Friday & Saturday); you will find the cheapest international airfare deals if you travel midweek, usually departing and returning on a Tuesday or Wednesday.
Spend Saturday night
Business travelers fly home on the weekend, so most discounted international airfare deals require a Saturday night stay. So be prepared to spend Saturday at your destination (party time!)
Don’t book too Early or Too Late
When it comes to cheap international airfares, you have to follow the Goldilocks rule: Don’t book too early or too late. We all know that an international ticket booked with less than 3 days notice will be very expensive, but it will also be pricy if you book too far in advance. Most airlines start competing for passengers around three to four months before departure; this is known as the “Goldilocks Zone”. Search for your international airfare about three to five months out and you will be in the best position to hit the international airfare deal jackpot.
Fly Trough the Side Door
If your desired destination is sold out (too expensive), try flying out of a secondary international airport (Boston vs JFK or San Francisco vs Los Angeles). The same works with your destination airports; If London is sold out (expensive), try Brussels, Amsterdam or even Stuttgart. You can use the savings to book a low cost inter Europe flight to London or you can jump on the Eurostar train from Paris or Brussels.
Fly Seasonally
Most budget travelers never fly during high season. They take advantage of the lower airfares and decent weather during the ‘shoulder season’. Europe’s fall shoulder season starts around September 15th and extends until the middle of November. It’s spring shoulder season starts in mid February and extends until the end of April. For the cheapest deals to New Zealand and Australia, fly in mid August, their fall and winters are quite mild and still allow you to enjoy the many outdoor adventures available Down Under. For Asia, fly from late September through November to get the lowest airfare deals. South America’s low season is anytime it’s not Christmas, New Year’s, Carnival or a school holiday.
Use the Multiple Flights Function
Vayama has a ‘multiple flights’ function on it’s ‘find a flight’ box. It’s a good idea to use it because it may be cheaper to fly into one city and return from another (for example; New York to London, returning from Amsterdam). Play around with different combinations and save.
Add a Stopover and Save
Direct flights (those with one stop) are also cheaper than nonstop flights, particularly when you fly long haul. For example the fares for a New York to Johannesburg flight will be cheaper on airlines that add a stopover (usually in Europe, Africa or the Middle East) versus the nonstop option from New York. The same applies to long haul flights to Asia. One stop in Seoul or Taipei could shave hundreds of dollars off an India trip when compared to nonstop flights.