FedEx will spend $2 billion in “initial investments” to become carbon neutral by 2040, the company announced today. The move comes as many of the world’s biggest automakers are also pledging to phase out carbon-emitting vehicles within the next several decades.

FedEx claims it is the largest cargo airline in the world, with more than 650 aircraft in operation. As such, it has a particularly large carbon footprint, making its pledge to go completely carbon neutral a uniquely massive challenge.

The money will be spent in three key areas: vehicle electrification, sustainable energy, and carbon sequestration. FedEx will also donate $100 million to Yale University’s efforts to devise new ways to achieve carbon sequestration, which is the process of capturing and storing CO2 from the atmosphere. The company said that, initially, it will fund research to help “offset greenhouse gas emissions equivalent to current airline emissions.”

But most of the funds will be spent on buying new electric delivery vehicles to replace FedEx’s largely gas-powered fleet. The phase-out will take place over the next several years, with the goal set for 50 percent of FedEx Express pickup and delivery vehicle purchases to be electric by 2025. By 2030, 100 percent of those vehicle purchases will be electric.

But the real challenge will be to eliminate the carbon output of FedEx’s air operation. While UPS is known for its ground delivery service, FedEx is mostly recognized for its global air express freight. And while there has been a lot of progress in rolling out new electric ground delivery vehicles, the process for eliminating emissions from the aviation industry has been much slower.

That’s probably why FedEx’s goal of becoming completely carbon neutral is so far off in the future. Global automakers like Volvo, Ford, General Motors, and others have set similar deadlines within the next decade. But electrifying ground vehicles is simple compared to building a fleet of non-polluting airplanes.

FedEx currently operates 118 all-electric trucks and 364 commercial hybrid trucks, the company says. That is a tiny fraction of the overall 43,000 motor vehicles the company has in operation currently.

The company says it will also seek to eliminate the carbon produced by its packaging and shipping facilities. This can be achieved through “carbon–neutral shipping offerings and sustainable packaging solutions,” as well as investments in renewable energy.

Notably, FedEx did not say it would purchase carbon offsets as a way to achieve full neutrality, though its investment in Yale University’s research project could be seen as such. Purchasing offsets has become a standard way for car companies and other businesses to write off their carbon emissions by investing in renewable energy or conservation projects aimed at bolstering forests’ ability to naturally store carbon. But there’s growing evidence that offsets haven’t succeeded in slowing global warming and have instead given companies license to keep polluting.

FedEx, which is based in Memphis, Tennessee, is the latest giant corporation to make a specific pledge to go carbon neutral. United, Delta, and JetBlue said they would eliminate all of their emissions over the next several decades. And Uber and Lyft have pledged to go carbon neutral within a similar timeframe.