Delta Air Lines says it will become the first U.S. airline to give customers the option of buying trees to help offset carbon emissions associated with their air travel. To kick off the program, Delta is making a donation to The Conservation Fund for every customer taking a Delta mainline or Delta Shuttle flight on Earth Day, April 22, and is pledging a commitment to plant a tree for each of the airline’s 47,000 employees.

Beginning June 1, customers who purchase a ticket online will have the option to contribute toward the offset of carbon emissions associated with air travel through a donation to The Conservation Fund. Contributions of $5.50 for a domestic roundtrip flight and $11 for an international roundtrip flight will be used to plant trees throughout the U.S. and abroad. A small portion of the donation will also supports the organization’s education and outreach efforts.

Delta has launched an email campaign to promote the initiative.

Other airlines, including Cathay Pacific, Virgin Blue, and SAS have similar programs.

British Airways has taken some heat for not putting enough marketing muscle behind its voluntary program.