At 19 hours, it’s the world’s longest flight. But how will the human body cope?

Regular nonstop flights between the east coast of Australia and London or New York could soon become a reality – and in preparation, Australian airline Qantas has announced the first of three test flights will takeoff this Friday.

The aim? To see how the human body copes with 19-20 solid hours of air travel.

This inaugural test flight, operated by a Boeing 787-9 Dreamliner, departs New York on October 18 and is due to arrive in Sydney Sunday morning, local time.

On board will be 40-50 “guinea pig” passengers, pilots, crew, scientists and medical experts.

Most of the people on board the test flights will be Qantas employees, but there will be six Qantas Frequent Flyer volunteer passengers as well.

Qantas previously announced its goal of operating direct flights between London, New York, and three Australian cities – Sydney, Brisbane and Melbourne – by 2023.

Bjorn Fehrm, an aeronautical and economic analyst at Leeham News, tells CNN Travel there are several reasons travelers find the ultra-long-haul flight appealing, as opposed to a more typical two-part journey stopping in Dubai or Singapore.

There are no layovers, no extra journeys through customs and no transfer stress, he says.

“You can plan it so you fly overnight, and you could arrive to actually have a productive day the next day as well,” says Fehrm. “It’s going to be businesspeople that fly this way.”

If the 19-hour flight becomes a reality, it’s likely to cost travelers more.

“It’s cheaper for the airline to do two separate flights,” Fehrm says. “But some people are prepared to pay the extra price of that ticket.”

The next test flight will take place in November, from London to Sydney, and there will be another New York to London flight happening before the end of the year.

After the test flights, the new planes will enter commercial service.

Researchers from Sydney University’s Charles Perkins Centre, Monash University and the Alertness Safety and Productivity Cooperative Research Centre – a scientific program backed by the Australian government – will examine the impact of the long flight on those on board.

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Passengers in the main cabin will wear monitoring devices, and experts from the Charles Perkins Centre will study how their “health, wellbeing and body clock” are impacted by a set of variables that include lighting, food and drink, movement, sleep patterns and inflight entertainment.

Passengers have been advised to keep a daily log in the lead up to the flight and for two weeks after, to show how they feel and how they’ve coped with jet lag.

Pilots and cabin crew will also be monitored and keep sleep diaries. Cameras will be mounted in the cockpit to record pilot alertness.

“People seem to be wildly different when it comes to the experience of jetlag – and we need more research on what contributes to jetlag and travel fatigue, so we can try and reduce the impact of long-haul flights,” Professor Stephen Simpson, academic director of the University of Sydney’s Charles Perkins Centre, tells CNN Travel.

“We have a long way to go in terms of understanding how the wide variety of influences – including nutrition, hydration, exercise, sleep and light – might work together for maximum benefit.”

Simpson says the research undertaken on these test flights will help the science and aviation industry gain a great understanding of the impact of long haul flights on passengers and crew.

Monash University scientists will focus on the flight crew, recording their melatonin levels before, during and after the flights, as well as studying brain wave data from electroencephalogram devices worn by the pilots.

This information will then be shared with the Civil Aviation Safety Authority “to help inform regulatory requirements associated with ultra-long-haul flights,” Qantas said in a press release.

“Ultra-long-haul flying presents a lot of common sense questions about the comfort and well-being of passengers and crew,” says Alan Joyce, Qantas Group CEO, in the release.

“These flights are going to provide invaluable data to help answer them.

“For customers, the key will be minimizing jet lag and creating an environment where they are looking forward to a restful, enjoyable flight. For crew, it’s about using scientific research to determine the best opportunities to promote alertness when they are on duty and maximize rest during their down time on these flights.”

Dr. Eileen McNeely, co-founder and director of the Harvard T.H. Chan School of Public Health Sustainability and Health Initiative for NetPositive Enterprise (SHINE) and instructor in the department of environmental health, tells CNN Travel that the health impacts passengers could face on super long haul flight are similar those on shorter flights, but increased.

“Exposures that are taxing on the body will still be present – but for longer times,” McNeely explains.

“Passengers will still face possible hypoxia, dehydration, muscular aches from lack of mobility, exposure to loud noise, jet lag, exposure to cosmic radiation and possible cabin air contaminants. These conditions pose a greater threat for vulnerable passengers with underlying diseases that already cause these problems.”

However McNeely points out that the advances that made ultra-long haul flights possible – namely lighter and more efficient aircraft – translate to more tolerable environmental conditions, which will help.

Higher cabin pressures, increased humidity and quieter engines will also improve the situation, she says.

Still, McNeely expresses concern about restricted mobility, advising those on board to get up and move about the cabin frequently and increase intake of fluids – except for alcohol, due to the dehydration effect.

“If you are over 60 with underlying cardiopulmonary disease, see a physician for medical screening including tests for oxygen saturation, in case you need supplemental oxygen aboard the aircraft,” she adds.

As for the cabin crew, McNeely recommends the airline monitor their health over time, given the increased exposure to cosmic radiation and noise, as well as ensure air crew get sufficient rest periods before, during and after flight.

For some, the prospect of a 19-hour nonstop flight might sound unbearable.

“It was very much doubted in the previous generations of aircraft that this was something you’d want to do and that could be economically beneficial for airlines to do,” Fehrm tells CNN.

If the flight comes to be, it’s unlikely to significantly change the aviation industry, he says, pointing to the existing 17-hour flights between Singapore to New York operated by Singapore Airlines.

“In the world, we have 20,000 aircraft flying every day, and there are nine aircraft doing this kind of flight,” he explains.

“It’s an outlier for a very select group of people – a prestige project,” he says. “But it definitely makes sense in certain circumstances, and then it would be worth the cost.”

CNN’s Francesca Street contributed to this report.