LONDON >> Australian airline Qantas is preparing for what could become the world’s longest direct commercial flights — around 19 hours nonstop to Sydney from New York and London — with three test runs to monitor the effects of so-called ultra-long-haul journeys on the body.

Some 40 people, including pilots, crew members and passengers, will become onboard guinea pigs for two test flights from New York to Sydney and one from London to Sydney, the airline said Thursday.

According to Qantas, this will be the first time that a commercial airline has flown nonstop from New York to Australia and only the second direct London-to-Sydney commercial flight.

It plans to conduct the test flights in October, November and December, with a target of starting regular services to New York and London from Australia’s east coast as soon as 2022.

Those routes would exceed the approximately 9,500-mile, 18 1/2-hour length of Singapore Airlines’ service between Singapore and Newark, New Jersey, currently the world’s longest commercial flight and one of a host of super-long-haul routes made possible by lighter and more fuel-efficient aircraft.

Teams of scientists and medical experts will be closely observing the physical and mental effect of the lengthy journey spent in the confines of an airplane cabin.

“The risk of travel fatigue is higher because the flights are longer,” said Svetlana Postnova, a senior lecturer in neurophysics and brain dynamics at the University of Sydney and one of the researchers working with Qantas to study the effects of the ultra-long-haul flights on passengers.

Passengers will wear smartwatches, allowing researchers to track how the flight affects their body clocks and how quickly they are able to recover from jet lag.

Qantas will offer exercises to improve blood flow, guided meditation, and a tailored schedule of meal times and lighting to make their experience in the air more bearable and help passengers avoid being floored by the adjustment to a new time zone.

“We hope that people will be much better off arriving to their destination compared to if they have to take connecting flights,” Postnova said in a phone interview. “We anticipate that with our optimized schedule, the direct flights will be better in terms of jet lag, well-being and how you feel on board.”

The pilots will be closely monitored, too, with electroencephalogram, or EEG, tracking of their alertness, and tests on their level of melatonin, a hormone linked to regulation of the body’s circadian rhythms.

The data will be used to devise what schedule of work and rest will suit the pilots operating the extra-long routes.

With airlines such as Qantas and Qatar Airways already operating 17-hour flights, Kit Darby, an aviation consultant, said pilots were likely to adapt quickly to even-longer flights.

“If pilots are regularly doing 16- or 17-hour flights, it is not a dramatic difference,” said Darby, a former United Airlines captain and Boeing flight instructor. “They will feel it, but it is manageable.”

Longer nonstop routes have an appeal for both airlines and passengers, Darby said.

“For airlines, the most efficient way of flying an airplane is to fill it up and fly it as far as it will go,” he said. “And from a passenger point of view, it is great to go directly where you want to go to without problems such as missed connections.”

Aviation fanatics who want to get their hands on a ticket for the New York or London to Sydney test flights will be disappointed, however. Qantas said it would use mostly its own employees to make up the passengers and crew, and no seats would be sold.

Ensuring crew members and passengers can be comfortable on a 19-hour flight is not the only challenge facing Qantas.

The Boeing 787-9 airplanes that will be used for Qantas’ test-runs are capable of carrying close to 300 passengers but will only carry a maximum of 40 people for the tests. The airline said this was in order to minimize weight. Qantas has not yet chosen which plane would be used for the commercial flights, but Airbus and Boeing have both proposed aircraft.

At a time when the aviation industry is under scrutiny for its effect on the climate, Qantas said that the carbon emissions from the research flights would be fully offset.

And even if the test flights go off without a hitch, Qantas would still need to seek regulatory approvals.

The airline says it expects to make a final decision about “Project Sunrise” — as it calls the proposed flights — by the end of this year.

“Flying nonstop from the East Coast of Australia to London and New York is truly the final frontier in aviation, so we’re determined to do all the groundwork to get this right,” the Qantas Group’s chief executive, Alan Joyce, said in a statement.

© 2019 The New York Times Company