Delta will spend more than $100,000 to offset the greenhouse gas emissions of every flight to and from Las Vegas, Nevada, this week. It’s an effort to reduce the environmental impact of people flying in for the Consumer Electronics Show that’s taking place, which is expected to bring in 170,000 people from 160 countries between January 7th and 10th.

To make those flights carbon neutral, Delta will put that money toward planting trees and helping farmers grow their crops more sustainably in Kenya and Uganda. It’s investing in an initiative called The International Small Group & Tree Planting Program, which says it has planted more than 19 million trees since 1999. 

Delta’s announcement comes on the heels of JetBlue becoming the first airline to commit to making all of its domestic flights carbon neutral starting in July. Both airlines are responding to growing concerns about how flights contribute to the climate crisis. Teen climate activist Greta Thunberg has helped ignite a global phenomenon of “flight shaming” as she committed to traveling by train and boat rather than flying internationally to attend United Nations climate talks. Currently, 2 percent of global carbon dioxide emissions come from aviation, and that number is expected to climb. Emissions from the sector have grown by 32 percent in just the past five years, according to a report by the nonprofit International Council on Clean Transportation.

Airlines and passengers can make up for the pollution they’re generating by purchasing offsets that help to keep planet-heating greenhouse gas emissions out of the atmosphere. Often, that’s by planting trees that breathe in and store carbon dioxide. But tree-planting schemes can be complicated. Trees need to keep the carbon dioxide they’re storing for about a century (the amount of time the carbon would have stayed in the atmosphere) in order for them to effectively help slow down climate change. Otherwise, they just spit the carbon back out into the atmosphere. And offsetting a flight shouldn’t be an excuse for flying more or not taking additional efforts to actually cut down on emissions. 

Yet, despite the drawbacks of relying on offsets, it is notable that airlines are actually doing something about climate change. One of the critiques of the “flight shaming” phenomenon is that it could place too much blame on individuals rather than holding big polluting industries responsible. “The more we talk about the relative merits of individual action versus more systemic and political action, the more we aren’t talking about the questions that are maybe more important,” Natalie Jones, a PhD student in international law at Cambridge University and a staff writer at the International Institute for Sustainable Development, told The Verge in September.

For its part, JetBlue is trying to shrink its carbon footprint on top of buying offsets. For all flights leaving San Francisco starting mid-2020, it says it will use fuel with lower emissions made from food waste (in particular, used cooking oil and animal fats). It’s also replacing older planes with more efficient aircraft. The company’s annual carbon emissions reached over 10 million metric tons in 2018, which is a little under what three coal-fired power plants might put out in a year.

Delta, one of the largest airlines in the world, is also moving to more fuel-efficient planes and has committed to slashing its greenhouse gas emissions in half by 2050. Over the past several years, the company has worked to keep its annual greenhouse gas emissions from rising above 2012 levels. Each year since, they emitted roughly 40 million metric tons of carbon dioxide, which is equivalent to the annual pollution of about 10 coal-fired power plants.

“We reduce where we can and offset where we can’t. By offsetting all of our domestic flying, we’re preparing our business for the lower-carbon economy that aviation – and all sectors – must plan for,” Robin Hayes, JetBlue’s chief executive officer, said in a statement this week.