(CNN) -- Two beloved giant pandas left the United States for their new homes in China on Thursday.
Three-year-old Mei Lan left Zoo Atlanta in Georgia early Thursday morning and was flown to Washington aboard a FedEx 777 christened the "Panda Express."
In Washington, the plane picked up Mei Lan's 4-year-old cousin, Tai Shan, who left Washington's National Zoo.
The pandas, which were on loan from China, are being repatriated to help replenish the endangered species' numbers. They will eventually take part in a breeding program in China. The National Zoo estimates that 1,600 giant pandas are left in the wild.
Kathleen Ryland of Highland, Maryland, brought her children to say goodbye to the Washington giant panda.
"We watched him as he grew up, and it's kind of sad to see him go," Ryland said.
The flight from Washington to China will be about 15 hours, said Dave Bronczek, president and CEO of FedEx.
A panda breeding center that one of the pandas was heading to was preparing, according to the newspaper China Daily.
Officials at the center were searching for a boyfriend for Mei Lan, the paper reported.
They were also searching for a Chinese language teacher so that Mei Lan could be taught to understand when she is told in Chinese to return to her cage.
"Mei Lan has been living in the United States since she was born, and she must be unfamiliar with Chinese, especially the Sichuan dialect," Huang Xiangming, a director of the breeding center, told the paper.
Tai Shan is headed to a different facility in China's Sichuan province.