Delta Air Lines became the first major air carrier Thursday to make same-sex domestic partners whole for additional income taxes they owe for health care plans.

Atlanta-based Delta will pay those taxes for employees retroactive to Jan. 1. The tax is only a problem for employees living in states that do not recognize their marriages; Georgia is one of them. Delta executives, pilots, flight attendants and other employees living there have to pay extra tax based on the value of the insurance.

There are currently 37 states that allow same same-sex marriage. The U.S. Supreme Court is expected to issue a ruling by the end of June that could expand same-sex marriage to the entire country.

Delta Air Lines Inc. is hardly the first major company to offer such benefits, known as “grossing up.” There are at least 40 large companies and law firms that make employees whole for the tax, according to the Human Rights Campaign Foundation, which lobbies for LGBT rights. The group says Delta is the first big airline to do so.

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Grossing up has become less of an issue as more states allow same-sex marriage, according to Deena Fidas, director of the group’s workplace equality program.

Still, she says, “it’s the right thing to do. It’s fair to the workforce.”

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