Why flying on Christmas Day is cheaper: Australian crosses International Date Line to get three Christmases

Those flying with Qantas on December 25 can indulge in festive fare ranging from prawn or turkey rolls to special Christmas cocktails, with a lucky few even scoring a free set of exclusive "Roodolph" Qantas pyjamas.

Additionally, as part of the airline's month-long festive initiative, passengers could win $200 flight vouchers, lounge invitations, and Tim Tam gift packs while flying. There will also be roving Christmas carollers in terminals and a Santa's Grotto awaiting younger customers in its Sydney and Melbourne departure areas.

Jetstar staff will be sporting special red hats and reindeer ears for the holiday, as well as giving children festive headbands and colouring-in sheets.

Virgin Australia will be bringing back its Santa request forms for children, among other initiatives throughout December.

"Our crew will personally deliver them to Santa. We will also have crew Christmas carollers and fun giveaways for children," a Virgin spokesperson said.

This airline is also doing social media Christmas giveaways, and adding festive touches to cabin crew uniforms.

Many flyers, like Hendrickson, will also be hoping for a less-packed flight and less-crowded airport on the day.

"I've heard a mix of things but I'm hoping it'll be nice and quiet; I've checked seat assignments for the flight and most seats are spoken for, so we will see just how packed and busy my particular flight and the airport will be," she said.

Although the Christmas school holiday period is one of the busiest times of the year for airlines – Qantas alone estimates it will fly around 800,000 passengers over the two-week Christmas and New Year period – historically, flights on December 25 itself dip in both demand and price.

The US-based mum was able to buy her round-trip Seattle-Melbourne flights for US$2400 ($A3600) – a significantly cheaper price than if she flew on the days prior.

"It was $800 cheaper to fly on Christmas," said Hendrickson. "That was a selling point for me as I booked the flight only three weeks in advance."

Canstar's Steve Mickenbecker said that, although Christmas Day economy flights are currently priced between $2000-$5000 each way in the week prior, consumers who book their flights early can typically expect to pay less compared to the days either side of the date.

"Generally, people want to have Christmas with family and friends so they tend not to want to fly on Christmas Day, so you'd expect demand to usually be down for that day relative to the surrounding dates," said Mickenbecker.

Expedia's Daniel Finch said it's a simple case of supply and demand.

"Airlines set airfares based on demand, and as many travellers typically avoid flying on Christmas Day thanks to family commitments, it's usually when you can find the best deal," said Finch. "You'll also likely find fewer crowds at the major airports, so wait times may be much shorter."

Some past airline Christmas Day initiatives have included: Japan Airlines serving KFC as an inflight meal (the chain's fried chicken is a popular choice in Japan at Christmas), Qatar Airways and Singapore Airlines serving turkey on board, Thai Airways offering passengers Christmas dessert, and Cathay Pacific putting on an elaborate festive spread of roast turkey, pork belly, traditional pudding and all the trimmings for those who visit its Hong Kong lounges.