As the world moves toward a zero-carbon economy, the airline industry faces a challenge: They create enormous amounts of emission on each flight, and while some tiny electric planes are beginning to fly now, it’s much harder to shrink emissions in larger jets. Now United says that it plans to account for part of its carbon footprint through the use of another emerging technology: carbon capture plants that pull CO2 directly from the atmosphere.

The airline announced today that by 2050, it plans to reduce its greenhouse gas emissions by 100%, and it’s the first major company with a plan to do that without the use of carbon offsets such as tree planting. United CEO Scott Kirby says that the company is aiming to be what it calls “100% green” rather than to reach “net-zero,” a goal that is common in other corporations.

“One of my long-standing frustrations with climate change is that even the people who do care and want to make a difference allow themselves to take the easy path,” Kirby said on a press call. “Unfortunately, it’s just not that easy. While there are some laudable traditional carbon offset programs, the reality is that traditional carbon offset programs simply can’t come close to offsetting the 4,000-times increase in annual carbon emissions since the industrial era began. It is just mathematically impossible to find enough land to plant 4,000 times as many trees, as an example. When every single corporation uses carbon offsets as their way to get to net-zero, even when some of those are good projects, they really aren’t solving the problem at all.”

United is now making an initial multimillion-dollar investment in 1PointFive, a company that is licensing direct air capture tech from Carbon Engineering, one of the startups pioneering the new technology. At full capacity, a single direct air capture facility could capture a million tons of CO2 in a year, as much as around 40 million trees in the same time period. The CO2 would be permanently stored deep underground by Occidental, the oil company, which is the major partner behind 1PointFive. (Ironically, after decades of drilling for fossil fuels, oil companies are now partially getting in the business of returning carbon to the ground. Occidental, which also aims to get to net zero emissions by 2050—including for its customers’ emissions—now talks about becoming a”carbon management” company.) The airline will later invest in additional plants, but even a single plant could get close to eliminating nearly 10% of the company’s annual emissions.

United is also working on directly cutting its own footprint. The company already uses alternative fuel on some flights. At LAX, for example, it uses sustainable aviation fuel made in part from agricultural waste and nonedible natural oils. Still, even if that fuel was used in every flight, it couldn’t fully eliminate emissions, and alternative fuels have proved hard to scale up. While United plans to continue to invest in the technology, it’s not a full answer. And truly zero-emission, long-haul jets aren’t yet on the horizon. Small electric planes can handle shorter flights, but batteries or hydrogen are still impractical for heavier aircraft. It’s possible that technology will radically improve before the middle of the century, but the airline is planning for a scenario where it will still have to burn unsustainable fuel.

Kirby says that the project was a priority for the company even as it continues to take a financial hit from the pandemic. He now hopes that additional companies, including other airlines, will also take the step to invest in direct air capture and sequestration rather than traditional offsets. “The only way this is going to work for the globe, of course, is if others join,” he says.