FedEx (NYSE: FDX) transported six giant pandas between the United States and China this week on what the company calls the “FedEx Panda Express.” FedEx transported female Lun Lun and male Yang Yang, both 27 years old, from Hartsfield-Jackson Atlanta International Airport to Chengdu Shuangliu International Airport along with their twin female offspring, Ya Lun and Xi Lun. Lun Lun and Yang Yang had lived at Zoo Atlanta since 1999; their cubs were born in 2016. They were moved to the Chengdu Research Base of Giant Panda Breeding.

The company has worked with Chinese government officials for more than 20 years to transport giant pandas to and from China. The first FedEx panda flight was in 2000.

The company brought pandas Bao Li and Qing Bao, both 2, from China to the Smithsonian’s National Zoo and Conservation Biology Institute in Washington on Tuesday. Bao Li is the grandcub of Mei Xiang and Tian Tian, whom FedEx transported to China, along with their cub, Xiao Qi Ji, in November.

FedEx donated the transportation cost. Animal care experts from Zoo Atlanta and the Smithsonian zoo were on the flights. The pandas traveled with bamboo, water and treats. “Each giant panda move is special, and we’re always honored when selected as the trusted transportation provider,” said Richard W. Smith, chief operating officer, international, and chief executive officer, airline, at FedEx.

Bao Li and Qing Bao are quarantining ahead of their public debut on Jan. 24.