Is there a future for ultra-long-haul flights in a world without CO2 emissions?

This year, Qantas announced two plans that are in direct conflict.

In March, Australia’s largest aviation group went public with the admirable goal of achieving net-zero emissions by 2050 and a 25 percent reduction by 2030 through new clean fuels, increasing efficiency, and using CO2 -compensations.

This was a turning point for the airline industry, with cutting-edge detail and bold links between executive pay and improved sustainability.

But two months later, Qantas confirmed its order for 12 new Airbus aircraft capable of operating ultra-long-haul flights, enabling non-stop flights from Sydney and Melbourne to London or New York.

What is the conflict? These long-haul flights have to carry considerably more fuel and, therefore, fewer passengers, making them significantly less efficient.

If the airline industry goes down this road, it will be a step backward in the fight against climate change.

While Qantas plans to make these flights carbon neutral, this will have to come with carbon offsets as there are currently no other options.

Is there a future for ultra-long-haul flights in a world without CO2 emissions?

Flights like this will come under scrutiny as the world gets more serious about climate action.

Qantas has confirmed an order for a dozen Airbus A350-1000 aircraft to operate the world’s longest flights. Photo: Getty

Flying the furthest involves costs.

For decades, Qantas has hoped to overcome the Australian tyranny of distance by starting ultra-long-haul flights as early as 1989.

However, these tests did not translate into regular flights, leaving the door open for the main competitor Singapore Airlines, which currently has the two best ultra-long flights in the world.

Qantas seems determined to change that.

In 2025, the airline’s new non-stop Sydney-London flight will travel 17,800 kilometers non-stop to become the world’s longest flight.

While it may seem like a single flight would reduce emissions, the opposite is true.

The most efficient flights (based on burned fuel per kilometer) are those between 3000 and 5000 kilometers, depending on the aircraft type. In contrast, non-stop ultra-long flights produce more CO2 emissions than two shorter journeys with a stopover.

The reason is simple physics. Aircraft flying ultra-long distances need to have a lot of fuel on board, especially on takeoff, to complete the later stages of the journey. The new planes ordered by Qantas will require about 0.2 kilograms of energy to carry one kilogram of 1,000 miles.

Given the long distance, this means that it is not very economical with fuel. Not only that, but the high fuel load also means less space for passengers.

This gives an even less favorable result based on the metric of carbon dioxide emitted per passenger kilometer. For example, a non-stop flight from Auckland to Dubai of 14,193 kilometers produces 876 kilograms of CO2 per person in economy class. At the same time, the same journey with a stopover in Singapore would yield 772 kilograms.

Exact emission rates may differ due to flight paths, cargo weight, and weather, among other things.

So while a typical A350-900 can hold 300 to 350 passengers, Singapore Airlines’ existing marathon flights with these aircraft can only carry half that, namely 161 passengers.

Similarly, the scheduled Qantas flights would have just 238 passengers, 112 to 172 seats less than what Airbus recommends.

As you might expect, fewer passengers increase ticket costs, and these flights become more exclusive, adding to the problem that a small wealthy elite disproportionately impacts the environment.

Can long-distance ever be low-carbon?

Non-stop marathon flights stand in the way of a broader shift to a low-emission world.

If airlines are serious about their industry’s growing contribution to fossil fuel emissions, they should research alternative fuels and technologies through programs such as the EU’s Clean Sky.

These programs have shown that sustainable fuels and new technologies are much better suited for shorter flights.

Electric aircraft, for example, will become viable for short-haul flights shortly. In Sydney, electric seaplanes will soon enter the short-hop sector. At the same time, hybrid-electric technology has the potential to support flights of up to 1500 kilometers, subject to advances in battery technology.

Electric aircraft are a good solution for short flights.

What about the long distance, then? We have two options. One is hydrogen, and the other is sustainable jet fuel.

While there is a huge hype around clean hydrogen, the reality is that green hydrogen, derived from renewable electricity, only makes up 1 percent of all the hydrogen we produce. We would need a massive effort to scale up to meet aviation demand.

Another challenge is the low energy density of hydrogen, which means that the flight range is estimated to be up to 7000 kilometers by 2040.

As a result, sustainable aviation fuel remains the only option for long-haul flights. The aviation industry is pinning its hopes on fuels derived from biological raw materials (used cooking oil or oil derived from algae) or synthetically produced.

The sustainability of these fuels depends on the raw material, the production process (which will again require large amounts of renewable energy), and a detailed understanding of the effects on the atmosphere of any gases emitted.

That suggests that these fuels are likely expensive, with volumes difficult to come by to completely replace fossil fuels. Nevertheless, these fuels will have to be part of the future of aviation.

Algae-derived oil is one of the options for sustainable aviation fuels. Photo: Getty

New ways of traveling

How we think about flying is changing, with climate impact for many travelers in mind.

In response, some countries have begun to increase their focus and infrastructure spending on rail travel to encourage new travel patterns.

The growing regenerative tourism movement, which emphasizes a deeper commitment to place and people, indicates a real potential to shift mass travel from far and fast destinations to near and deep.

The role of flying in tourism is changing and will change even more in the coming years. Soon, electric and hybrid aircraft will encourage shorter flights in a low-carbon world. You can already see this in the trends towards more climate-friendly travel closer to home.

As for ultra-long-haul flights, it’s hard to imagine how they’re compatible with the goal of net zero emissions.

Susanne Becken, Professor of Sustainable Tourism and Director, Griffith Institute for Tourism, Griffith University Paresh Pant, Ph.D. Candidate and Session Academic, Griffith University

This article is republished from The Conversation under a Creative Commons license.

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