This gives a whole new meaning to the term cabin fever.

Australian airline Qantas is preparing to break the record for the world’s longest flight — pitching a staggering 19-hour nonstop journey between the Big Apple and Sydney.

The airline on Thursday announced they would run three tests flights later this year on two new routes — London to Sydney and New York City to Sydney — to see if the human body can handle being in the air that long.

But aviation experts warned it won’t be a pretty experience and said the routes would be targeted at time-poor, cash-rich business travelers.

“You don’t sit for 20 hours, neither do you sleep for 20 hours. It’s inconceivable” Bjorn Fehrm, an aeronautical analyst for Leeham News, told The Post.

“You’re not doing this because it’s a great experience, you’re doing this because you gain time,” he said.

A team of scientists on board will monitor the effect of ultra-long haul flights on 40 human guinea pigs made up of crew and passengers, measuring their melatonin levels, brain wave activity, body clock and sleep patterns.

The longest flight in the world currently operates between New Jersey’s Newark Liberty International Airport and Singapore and clocks in at 18 hours and 45 minutes.

Researchers will also be looking at how sleep patterns, food and beverage consumption, lighting and in-flight entertainment impact passenger’s body clocks and health.

Fehrm, a former fighter pilot in the Swedish Air Force, said direct flights are on average 20 percent more expensive than those with a stopover.

He added that ultra-long haul flights had proliferated in recent years because they were a prestige item for airlines and had little bearing on their bottom line.

Fehrm said Qantas would need to create new areas for people to stretch such as bars or dining areas to counter related health issues such as deep vein thrombosis.

“How do you make sitting for 20 hours in the same place agreeable?” he said.

“If you sit like that — especially in premium economy which doesn’t have lay flat seats — blood can gather in the lower part of your body, so they’d better try to have places where people can walk around and move.”

The airline said it would decide later this year if will begin operating the routes regularly, citing hurdles including employee unions and regulatory approvals.

This will be the first time a commercial airline has flown nonstop from New York to Australia, according to Qantas.

Aviation fanatics wanting to get their hands on a ticket will be disappointed — Qantas said it would use employees on the test flights and no seats will be sold.