Before their big move, the pair attended an elaborate farewell ceremony in their honor in China’s Sichuan Province on Wednesday, which U.S. and Chinese dignitaries attended along with San Diego Zoo Wildlife Alliance President and CEO Paul Baribaul and Todd Gloria, San Diego mayor.

Three-year-old female panda Xin Bao is “gentle and well-behaved,” while male panda Yun Chuan, 4, is “smart and lively,” the China Conservation and Research Center for the Giant Panda said in a statement, adding that the duo would enjoy “carefully prepared fresh bamboo, bamboo shoots, fruit, vegetables, and specially made steamed buns” during their flight.

The duo will also be accompanied by several experienced nutritionists and vets, and once at the zoo, the Chinese experts will stay for around three months to help the pair through the quarantine and adjustment period, the center added.

The pandas’ relocation is part of ongoing efforts between the two nations to protect the mammals, officials from both nations said. Pandas are no longer considered endangered but their status is listed as “vulnerable,” according to the World Wildlife Fund (WWF).

The animals are also star attractions in zoos in the United States — and have long been associated with China’s diplomatic efforts.

China is home to the only natural habitat for pandas, and panda diplomacy can be traced as far back as A.D. 685. Since then the mammals have been sent to nations around the world, serving as strategic goodwill ambassadors, attempting to soften China’s image abroad. In recent decades, China has lent pandas on renewable 10-year contracts for a fee, with all cubs born abroad to be sent back before they turn 4 years old.

The bears often become celebrities in the process — while the departure of three pandas from the Smithsonian’s National Zoo in Washington last year triggered tearful farewells and fears the United States would eventually be left with no pandas.

Yun Chuan is the son of Zhen Zhen, who was born at San Diego Zoo in 2007, the San Diego Wildlife Alliance said.

The pandas will be given “several weeks” to adjust to their new surroundings before going on display to members of the public, the alliance said, adding that the zoo would share information about how to see the duo once health care teams deemed the pandas ready to meet the public.

WWF estimates that just 1,860 giant pandas remain in the wild, facing threats that include climate change, loss of food supplies and habitat fragmentation.

“Although the conservation status of the giant panda is improving, there is still much work needed to ensure they remain on the path to recovery with healthy and flourishing populations,” the statement said.

Chinese wildlife officials said the loan of the two pandas would open a new round of panda conservation cooperation between the United States and China. The China Wildlife Conservation Association added that it hoped conservation efforts between the two countries would also lead to improvements in managing panda diseases, and help promote “friendship between Chinese and overseas peoples.”

It is not just San Diego that is eagerly awaiting a panda delivery.

Later this year, two new giant pandas will arrive in Washington, the Smithsonian’s National Zoo announced last month. The move came as a surprise, given the tense relationship between the United States and China, which owns and leases all giant pandas in U.S. zoos, The Washington Post reported at the time.

In fact, China’s pandas are so popular in Washington that one Chinese ambassador previously joked: “Many people don’t realize it, but there are actually two Chinese ambassadors in Washington: me and the panda cub at the National Zoo.”