Australian tennis legend Margaret Court is boycotting Qantas Airlines because its CEO Alan Joyce has taken a public stance in support of same-sex marriage.

‘As you will know, I have represented Australia many times and have the proud record of never losing a tennis match while playing for my country. I am disappointed that Qantas has become an active promoter for same-sex marriage. I believe in marriage as a union between a man and a woman as stated in the Bible,’ Court wrote in an open letter published in The Western Australian.

Court, 74, is one of only three women in tennis history to have won all four of tennis’ grand slam singles titles (Wimbledon, US, French and Australian) in the same year.

She has also won more grand slam singles titles (24) than any other women in history.

Court’s most enduring tennis rivalry was against the now-openly gay Billie Jean King with whom she squared off against multiple times at Wimbledon and other major tournaments.

It was Court who was responsible for King playing the most famous match of her career against Bobby Riggs.

Court had accepted a challenge to play the 1939 Wimbledon champion in early 1973 and lost badly.

King, who had fought to establish a women’s tennis tour, felt she had no choice then but to take on Riggs in the legendary Battle of the Sexes match. King won in straight sets. Married to a man at that time, King is now married to a woman.