JetBlue is giving up carbon offsets for its domestic flights, shifting its focus instead to sustainable aviation fuels. It’s a step that could help the airline actually reduce its emissions rather than relying primarily on controversial carbon offsets to counteract its fossil fuel use.

Back in 2020, JetBlue became the first US airline to voluntarily offset greenhouse gas emissions from all of its domestic flights. That effort ends in 2023, the company announced this week.

The airline now plans to effectively cut its per-seat emissions in half by 2035. For flights to take off without generating as much pollution, JetBlue says its planes will need to run on sustainable aviation fuels [SAF].

“JetBlue views SAF as the most promising avenue for addressing aviation emissions in a meaningful and rapid way – once cost-effective SAF is made available commercially at scale,” the company said in a December 6th press release.

Since 2020, JetBlue’s routes between San Francisco and Los Angeles have regularly run on sustainable aviation fuels. But the company’s eventually going to need a lot more SAF, which can be made from waste or crops like corn. It’s seen as a potential “bridge fuel” while electric planes and hydrogen-powered jets are still in development. JetBlue has inked deals with several companies to purchase more SAF, but it’s still in pretty limited supply and is more expensive than conventional kerosene jet fuel.

There are environmental challenges with SAF, too. Making and burning SAF still generates CO2 emissions. A lot of that CO2 is supposed to be canceled out by crops grown to produce the fuel, but there are also concerns about those crops leading to more deforestation.

Nevertheless, aviation is moving toward using more sustainable aviation fuels. The European Union has proposed requiring airlines to make SAF account for 5 percent of air transport by 2030, scaling up to 63 percent by 2050. European airline EasyJet also announced that it will stop offsetting its flights next year. Like JetBlue, it also plans to invest in sustainable aviation fuels and increase the fuel efficiency of its operations.

Carbon offsets are supposed to cancel out the pollution from burning aviation fuel by reducing emissions elsewhere — usually through investments in renewable energy or forestry projects that rely on trees’ ability to trap carbon dioxide. But years of investigations and research have found that most carbon offsets on the market don’t actually represent real-world reductions in pollution.

While JetBlue is dropping its carbon offset program for domestic flights, the company isn’t exactly turning its back on offsets. The airline still plans to purchase a “small quantity” of carbon offset credits to try to make up for emissions from a growing number of international flights, Bloomberg reports. JetBlue Ventures, a subsidiary of the airline, has also invested in carbon credit firm Rubicon Carbon.