A wave of ultralong flights that will get you halfway around the world in one hop is pushing airlines to deal with the one extra you can’t escape: Relentless insomnia, debilitating fatigue and tormented bowels, also known as jet lag.

Qantas Airways Ltd., which will start nonstop service between Australia and Europe this month, is working with scientists in Sydney to find ways to limit body-clock breakdown on the 17-hour flight. They’ve tried to make the color and intensity of the jet’s interior lights mimic dawn and dusk. Cabin temperatures and special meals aim to put passengers to sleep or keep them awake — depending on the time at the destination.

The Perth-London route is the latest endurance test as new aircraft technologies stretch the time a plane can stay profitably in the air. Delivery of a new Airbus model later this year will allow Singapore Airlines to resume its 19-hour marathon from Singapore to New York, an epic stress test for mind and body.

Key to the problem is circadian disruption — messing with 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 Steve Simpson, academic director of the Charles Perkins Centre, which is carrying out the research with Sydney-based Qantas. But there’s a baked-in biological catch: the clock can only reset by about 90 minutes a day, even in the right conditions.

The Qantas tieup 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’s no way to totally avoid jet lag.

For airlines, the stakes are huge. Qantas is taking eight 787-9 Boeing Co. Dreamliners and has options and rights on another 45, a total investment of about $15 billion at current prices.

Singapore Air has ordered seven ultra-long-range A350-900s from Airbus SE, listed at about $317 million each.

But that sunrise on Copacabana beach or the Champs-Elysees comes at a cost. Long-haul journeys increase the risk of a range of afflictions including depression and obesity, Simpson said. To learn more, his team will wrap monitoring devices around the wrists and thighs of about 20 passengers on the Perth-London flight on March 24 to see how their bodies cope.

On that route, lights nestled all over the cabin will be phased in over 15 minutes to soften the blow from jet lag, said Phil Capps, Qantas’ head of product planning &development. Blue light triggers wakefulness and yellow or orange tones encourage sleep, he said.

“To create that natural light on an aircraft traveling many thousands of feet in the air at a very fast speed requires a lot of science,” said Capps.