Some websites will tell you a Tuesday afternoon, others a Saturday.
"Between April 28 to May 4 says another, and "49 days in advance."
In fact, none of the above is true.
Airlines use yield or revenue management to maximise the revenue from each flight, and this is what sets the price.
Yield managers divide all the seats on a particular flight into different price levels, what the industry calls price buckets.
In times of high demand, an airline will assign fewer seats in the cheapest price bucket.
As these cheaper seats disappear, passengers will be left with more expensive options.
Yield managers monitor and adjust the number of seats in each bucket.
If a particular flight is experiencing lower demand than expected, the yield manager might move more seats into the cheaper price bucket.
Some travellers suggest if you wait until the last minute you can score a bargain airfare since airlines will drop prices to fill empty seats, but that's highly unlikely in today's world.
As the yield management strategy suggests, the cheaper seats are the first to go, and those who need to fly at short notice pay more.
Airlines earn far more revenue ar seat from late-booking passengers.
If an airline was to discount seats at the last minute to fill them it would compromise that lucrative business model.
Skyscanner's Best Time to Book Analysis and Momondo's Flight Insight are valuable tools that can help you pin down the best time to book flights.
Solo travellers prepared to cruise in shoulder or off-peak season can often avoid the dreaded single supplement.
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