Long haul travel just got longer with Australia's first direct flight to London via Perth taking to the sky with politicians, journalists and holidaymakers on board.

The flight — which takes 17 hours and 20 minutes — departed Perth International Airport about 7:00pm on Saturday and was scheduled to land at Heathrow Airport on Sunday at 5:10am (local time).

The Qantas Dreamliner 787-9 was designed to accommodate the long journey and has been touted as a boon for Australia's tourism industry.

Federal Tourism Minister Steve Ciobo said the route would act as a "gateway" to Western Australia and would have flow-on benefits for the rest of the country.

"For many international visitors the West Australian jewels have been off limits, not because it's been unavailable to them, but because it's been too hard to get to as there's been such a focus on the east coast.

"It's never been easier for people from the United Kingdom or more broadly across Europe to come to Australia.

"We have around 730,000 tourists who come to Australia and I am determined to grow their expenditure and grow their numbers."

The flight from Perth to London takes 17 hours and 20 minutes. ( Supplied: Qantas )

Qantas chief executive Alan Joyce said it was a "historic day".

"It'll be the first link between Europe and Australia that has ever occurred non-stop in aviation — we're so excited," Mr Joyce said.

"I think it's going to be fantastic for WA tourism because we always know when you have a direct service there is a significant increase in traffic."

WA Premier Mark McGowan said the route was a great opportunity to grow tourism jobs in the state.

Family unwittingly books on historic flight

Martina Dewberry and her husband John were on board the inaugural flight with their two children Isabelle, 5, and Sam, 3.

Martina, Isabelle, John and Sam Dewberry. ( ABC News: Emily Piesse )

Mrs Dewberry said the trip would be almost double their previous longest flight of 10 hours.

"We didn't actually plan to be on the first ever flight to London," Mrs Dewberry said.

"My travel agent asked us 'do you want to go straight or have a stop over?'. We said 'we'll take that [straight]'.

"When I talked to my mum she said 'when are you flying, the 24th? Well that's the first flight ever to London'.

"I got a little bit nervous but we'll be fine."

Mrs Dewberry said she planned to ease the journey by occupying her children with movies.