Found: the most expensive (and cheapest) day to book flights over Christmas

Travel insurance company Compare the Market has revealed the cheapest and costliest days to book one-way flights around the Christmas period.

If you're flying out of Sydney, Melbourne, Brisbane and Wellington, flights are generally cheaper from December 3 to 5, and 10 to 13, Compare the Market said.

Travellers can also save money by flying to select destinations in Australia and New Zealand from the four cities on December 31.

Hundreds of dollars can separate the cheapest and most expensive days to fly in December, the research showed.

The insurer used Skyscanner to compare ticket prices and found the most expensive prices were between December 20 and 22, and 26 to 29 across the four departure locations.

Flying from Sydney to Melbourne, at the time of comparison, buyers could find $51 tickets flying on December 3, 17 and 31 - almost $30 less than the average flight price of around $80.

This is compared to the most expensive flight from Sydney to Melbourne, on December 22, which cost $129.

Flights are generally cheaper than they were at the same time in 2023, the data revealed. The average flight out of Sydney is 6 per cent cheaper, and if you're coming from Melbourne, it's 14 per cent cheaper than December last year.

Melbourne Airport said to book as early as possible to get the best savings on popular destinations like Perth, Hobart and Darwin.

In general, when booking overseas destinations, the airport advises booking six to three months before you plan to travel.

International travel for Australians is on the rise. Year to date, the total outbound travel from Australia is 7 per cent higher compared to the same period in 2023, according to ForwardKeys.

In 2023, the number of international flights departing from Australia reached 22.7 million seats across 86.6 thousand flights, marking an 80 per cent increase from 2022, ForwardKeys said.