(Bloomberg) -- Richard Branson has long relished the image of the aviation pioneer, from traversing the Pacific in a hot-air balloon to making space travel available for paying customers. 

Now the British billionaire is participating in the first flight of a commercial aircraft across the Atlantic powered entirely by sustainable aviation fuel, beating arch-rival British Airways to the punch. 

Virgin Atlantic flight VS100 took off from London Heathrow to New York on Tuesday morning. Besides Branson and Virgin Atlantic Chief Executive Officer Shai Weiss, UK Transport Secretary Mark Harper will be on board the Boeing Co. 787, lending a political dimension to the exercise that seeks to show how the aviation world is cruising toward a cleaner future. 

But even Branson’s bravado and infectious optimism can’t mask that fact that the road toward net zero, a goal the industry aims to achieve by 2050, is becoming ever hard to navigate. SAF, as sustainable aviation fuel is called, isn’t available in large enough quantities to make a real impact. 

And airlines worry that the higher cost of the fuel will leave passengers footing the bill, just as they return to flying after years of pandemic malaise. 

SAF fuels are made from sources including waste oils and non-food crops and are widely seen as the only realistic short-term mechanism for the aviation industry to meet its sustainability goals.

With those feedstocks in short supply, scaling up will require fuels derived from electricity. The vast amounts of renewable energy needed are a stretch — leading to questions about SAF’s environmental credentials.

Deutsche Lufthansa AG CEO Carsten Spohr estimated in September that his airline alone would consume half of Germany’s entire electricity production to switch its fleet to green fuels like e-kerosene, underscoring the challenge in reducing emissions from air transport. 

For now, large passenger aircraft can’t switch to battery power because they lack the energy density for the foreseeable future to lift a commercial planeload of passengers and cargo into the sky. That leaves only alternative fuels as a viable option.

The Virgin Atlantic flight comes just a few days before the COP 28 climate summit kicks off in Dubai, which is also home to Emirates. The world’s largest international airline flew its own SAF flight last week, operating an Airbus A380 on a demonstration flight with one of its four engines powered by 100% sustainable aviation fuel. 

Harper, speaking to reporters ahead of the flight taking off, said the government sets the mandate while industry needs to “work out how to deliver it, negotiate the contracts and do the pricing.”

At the Dubai Air Show this month, Emirates President Tim Clark described the challenge of getting to even 10% of SAF fuel by 2030 as a “herculean” task. Still, he said, the industry would look for as much of the fuel as it could get as it will take a long time to decarbonize aviation through other means. 

The European Union has adopted mandates that will require airlines to use 6% SAF by 2030, rising to 34% by 2040 and 70% halfway through the century. Hurdles to getting there include the lack of availability and pricing, which currently sees airlines face fuel bills that are three to five times higher when they use the sustainable alternative. 

“It’s taken radical collaboration to get here and we’re proud to have reached this important milestone, but we need to push further,” Virgin Atlantic CEO Weiss said in a statement. “There’s simply not enough SAF and it’s clear that in order to reach production at scale, we need to see significantly more investment.”

The US has subsidized production of SAF with deep tax breaks. The UK has a target to have five SAF plants under construction by 2025, which Harper, the UK transport secretary, insisted at an industry event last week was “on track.” He said recent world events have shown the danger of over—reliance on energy imports as he pledged to build Britain’s SAF base.

British Airways owner IAG SA currently uses 1% SAF on its flights and said it would like to see more UK production and more incentives to drive the growth of the industry. 

“You need pretty deep pockets to do what the US is doing and the rest of the world isn’t going to be able to do that, but our overriding message to governments is that a mandate on its own won’t drive investment,” said Jonathon Counsell, IAG’s group head of sustainability. “You need policy incentives.”

--With assistance from Anthony Palazzo.

(Updates with quote from minister in 12th paragraph.)

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