Paris. A couple of star giant pandas who lived in France for 13 years and gave birth to three cubs were on their way back to China on Tuesday, the Beauval Zoo said.

Huan Huan, the female, and her partner Yuan Zi, both 17, are traveling on a 12-hour flight from Paris' Charles-de-Gaulle airport in big white boxes with windows, holes for breathing and the inscription “Bon voyage."

Zoo director Rodolphe Delord, during a goodbye ceremony at the airport, said “they are reaching an age that requires highly specialized care” and will “benefit from the optimal environment” at the Chengdu Research Base of Giant Panda Breeding, where they were born.

Delord had previously explained that Huan Huan has been diagnosed with kidney failure, which isn't uncommon for a carnivore this age. French and Chinese veterinary teams decided to send them back to China while their health condition allows them to travel safely, he said.

For decades, China has gifted friendly nations with its unofficial mascot as part of a policy of “panda diplomacy." The country now loans pandas to zoos on commercial terms.

The pair became famous in France since they arrived at the Beauval Zoo in 2012.

Huan Huan gave birth in 2017 to the first panda ever born in France, Yuan Meng, a male who was sent to China five years later.

She also gave birth to female twins in 2021, Huanlili and Yuandudu. They will stay for the time being at the Beauval Zoo, which welcomed 1.9 million visitors last year.

In Chengdu, the couple will “continue raising awareness of visitors about the conservation of this iconic species,” the zoo said.

There are about 2,000 pandas living in the wild in China and 500 in captivity worldwide.