You could say it’s the budget traveller’s holy grail: knowing exactly when to book a flight to get the cheapest fare. But now one flight comparison site, which analysed 7.5 billion airfares on its top 100 routes worldwide, believes it has found the answer.

According to the research by momondo.co.uk, the ideal time to book a flight is 53 days in advance, a move that may save an average of up to 29% on your fare.

Cheaper fares also depend on the time of the flight. Evening departures between 6pm and midnight are typically cheaper, while Tuesday is generally the cheapest day to fly.

For example, a flight from London to Lisbon, when booked 52 days in advance, costs on average £209 -compared to the average price of £287.

Flights from London to Dubai are cheapest 51 days ahead of travel, when it will cost £458 – 20% less than the average fare of £551.

As for the most expensive, fares are at their most costly three days before departure, while Friday is routinely the most expensive day to take to the air. It is also suggested that travellers should avoid afternoon flights if they are looking to save money.

“In general, it pays to book flights two months in advance,” says momondo spokesman Lasse Skole Hansen.

“We found these trends consistent across the board, so bargain hunters should consider flying at night and on a Tuesday, if they want to save money on their travels.”

Momondo’s research is consistent with previous studies into the age-old traveller’s dilemma of when to book. In January Skyscanner published the results of a three-year study, which found that on average five weeks in advance is the best time to find the cheapest fares.

However, Skyscanner also found this varies according to destination. The cheapest flights to Greece, for example, were found to be available just three weeks ahead of departure.

The new study by momondo.co.uk coincides with their launch of an interactive tool, Flight Insight, that allows travellers to assess the best time, day and season to travel.