Seven years after featuring astronaut Buzz Aldrin in its advertisements, Neste Oyj is once again gazing at the sky.

The Finnish company, whose bet on renewable fuels made it the best-performing large-cap in Finland over the past decade, has set its sights on a new market to conquer: aviation fuel.

The market is attractive, with the use of jet fuel growing 2% to 3% per year, despite more fuel-efficient planes, and as airlines seek ways to meet requirements to cut and offset emissions, Chief Executive Officer Peter Vanacker said in an interview at Neste’s seaside headquarters in Espoo, Finland, on Friday. About 300 million tons of aviation fuel is consumed annually around the world, Vanacker said.

“We have 100,000 tons of capacity available in that particular quality that the aviation industry needs, the supply chain is set up—all that is ready,” he’s said. “Now it’s about negotiating the sales contracts. We are already selling renewable jet fuel, but the volumes are at the early stages still small.”

Neste has about 15 memorandums of understanding with airlines and airports, and a number of sales negotiations ongoing, he said. As its team is still small and being ramped up, the focus is on “where we get the best traction” among airlines that are the most focused on sustainability, according to Vanacker.

The big hurdle is the expense. Renewable aviation fuel can cost as much as three times more than kerosene, Vanacker said. While some governments are forcing airlines to use more and more biofuel, kerosene is still exempt from tax due to a decade-old international agreement, meaning there are few incentives to move to renewable fuel.

“At the end, the customer has to have the willingness to pay,” Vanacker said.

But there’s really no alternative in the longer term.

“Electrification is still far away in aviation—I don’t see it in 2040, 2050,” he said. “And if it will come, it will be in short distances, and then the question is, is it better to fly or to take the train?”

Neste has been making renewable fuel, which it first called biodiesel, for more than ten years and is these days using waste and residues from the food industry to produce it, including used cooking oil and slaughterhouse waste.

After completing its Rotterdam and Singapore refineries in the early years of this decade, the product became profitable in 2013, propelling a share gain of more than 500% over the past five years. Neste is now expanding the Singapore facility, and the company’s capacity is set to increase to almost 4.5 million tons in 2022 from about 3 million tons now.

Vanacker is considering expanding the Rotterdam site or building a new facility in Finland or the U.S. as the Singapore facility is soon fully in use.

Neste’s renewables business has displaced traditional fossil fuels as the refiner’s profit engine. The renewables unit accounted for just about 20% of revenue last year, but almost 70% of adjusted operating income, while oil products brought in almost 70% of the company’s revenue, but generated only a quarter of its adjusted profit.

Last quarter, renewable margins fell from exceptionally strong levels in the prior quarters on higher feedstock prices and lower prices from new markets, alarming analysts. Vanacker sought to allay fears the margin decline is to stay.

“We’re running a very good business, we always try to do the best for our investors to make sure that we get good margins out of our products,” Vanacker said. “This is a growing market, we want to have a strong position as the No. 1 on a global basis, in those markets.”