SYDNEY • Qantas is trying to make the colour and intensity of the jet's interior lights mimic dawn and dusk.
Cabin temperatures and specially made meals will aim to put passengers to sleep or keep them awake - depending on the time at the destination.
The Australian airline, which has started a 14,500km Perth-London service, is doing all it can to minimise jet lag, or body-clock breakdown, on the 17-plus-hour flight.
It is not alone, as a wave of ultra-long flights that will get you halfway around the world in one hop are pushing other airlines to grapple with the issue too.
Emirates, Qatar Airways and United Airlines are part of the movement, with flights from the Middle East to New Zealand or Houston to Sydney.
The delivery of a new Airbus model later this year will allow Singapore Airlines to resume its 19-hour marathon from the Republic to New York.
What you can do is make sure you're pushing as quickly as you can to the destination time zone and getting the timing of things right. The way you feel, the way you function - mentally through to bowel movements - is all ultimately controlled by your body clock.
MR STEVE SIMPSON, academic director of the Charles Perkins Centre, which is carrying out research with Qantas
Key to the problem is minimising the toll on the internal body clock that regulates everything from brainwave activity to hormone production and cell regeneration.
The main cue for resetting that clock is light, said Mr Steve Simpson, academic director of the Charles Perkins Centre, which is carrying out research with Qantas.
But the clock can reset only by about 90 minutes a day, even in the right conditions. An ill-timed dose of sunshine or a badly chosen snack at the wrong hour can mean days of suffering, he noted.
"What you can do is make sure you're pushing as quickly as you can to the destination time zone and getting the timing of things right," he said.
"The way you feel, the way you function - mentally through to bowel movements - is all ultimately controlled by your body clock."
The Qantas tie-up with psychologists, nutritionists and sleep experts at the University of Sydney's Charles Perkins Centre highlights an uncomfortable truth about ultra-long-haul jet travel: There is no way to completely avoid jet lag.
But to fill the new long-range jets, Qantas and its rivals such as Qatar Airways, which flies from Doha to Auckland, need humans to better tolerate the effects of crossing the world in less than a day.
For airlines, the stakes are huge. Qantas, for example, is taking eight 787-9 Boeing Dreamliners and has options and rights on another 45.
And it does not end there.
As intercontinental air travel becomes affordable to more people outside the developed markets in Europe and North America, the demand for day-long direct flights is likely to soar.
Qantas has challenged both big plane-makers - Boeing and Airbus - to build a jet by 2022 that can fly 20 hours fully loaded from Sydney to London without a break.
Long-haul journeys increase the risk of a range of afflictions, including depression and obesity, Mr Simpson said.
To learn more, his team reportedly wrapped monitoring devices around the wrists and thighs of about 20 passengers on the Perth-London flight on March 24 to see how their bodies coped.
On that route, lights nestled all over the cabin will be phased in over 15 minutes to soften the blow from jet lag, said Mr Phil Capps, Qantas' head of product planning and development. Blue light triggers wakefulness and yellow or orange tones encourage sleep, he added.
While these very long flights have their own unique set of challenges, they can allow airlines to attract more higher-paying passengers in business class, who will pay a premium for the saving in time, said Ms Joanna Lu, Hong Kong-based head of Asian advisory at Flight Ascend Consultancy.
"Being stuck on an airliner for more than 18 hours is hard to bear," she added. "Unless you fly business."