"Tai Shan and Mei Lan not only represent the crystalization of American and Chinese cooperation to preserve pandas but also the friendship of the Chinese and American people," said Xie Feng, deputy chief of mission at the Chinese embassy in Washington in a farewell speech to the two pandas.
Tai Shan was born in Washington four-and-a-half years ago, to parents loaned to the United States by Beijing, and Mei Lan came into the world, the size of a stick of butter, at the Atlanta zoo three years ago.
But under agreements with the Chinese government, both were supposed to head to China when they turned two to join the panda breeding program.
Tai Shan's stay in the US capital was extended by two-and-a-half years, partly because Washingtonians had grown so attached to him but also because he was not yet ready at age two to be an effective contributor to the breeding program in China.
"Tai Shan's departure was postponed two times," Feng said in one of many speeches delivered by foreign and US officials to bid goodbye to the pandas at Dulles international airport.
"But he has grown into a handsome young man and it's time for him to go home now," said Feng.
But people in Washington and Atlanta were finding the departure of "their" beloved pandas, well, a bit hard to bear.
"This is the day all of us hoped would never come. Our boy, Tai Shan, is going to China," Steve Monfort, acting director of the National Zoo, said during a farewell ceremony at the airport.
Earlier in Atlanta, as Mei Lan was loaded onto the Panda Express the curator of mammals Rebecca Snyder called the female panda's departure "a bittersweet moment for the Zoo Atlanta family and for fans around the world."
But Thursday's departure was "a wonderful moment for giant pandas," added Snyder.
"We're very proud to have shared Mei Lan's life to the point where she can now begin making her own contributions to the world's population of giant pandas," she said.
Parties were held last weekend in "particularly cold and rainy" Atlanta for Mei Lan and amid a snowstorm in Washington for Tai Shan.
"I had to come see Tai one last time before he leaves," 50-something Jeanie Edwards told AFP at the National Zoo.
"I've been with him since he was born," Edwards said, speaking of Washington's panda as if he were a family member.
With his young female traveling companion already waiting inside the Panda Express in her own tubular steel crate, Tai Shan arrived in style at the airport, with a motorcade under police escort and helicopters hovering overhead.
Cameras clicked and whirred as he was wheeled in his crate into a cavernous freight hangar where security was as tight as it would be for a visiting dignitary.
After being weighed in his crate -- to be in compliance with federal weight-balance regulations -- Tai Shan was wheeled out to the waiting FedEx Boeing 777 for his big trip, on which he will be accompanied by a handler, a veterinarian and 75 kilograms (165 pounds) of bamboo for airplane food.
He paced back and forth in his crate and looked out at the crowd shivering on the tarmac before sitting down to munch on a bamboo shoot as his crate came to a halt at the rear of the plane.
"I'm sad he's leaving, but it's good that he's going home to help make more pandas," said nine-year-old Sarah Boyle, who was cutting class with her parents' blessing to see off the pandas.
Giant pandas are an endangered species, with only 1,600 of the black and white bears living in the wild.
Tai Shan and Mei Lan will go to separate refuges after their arrival in Sichuan province, which is home to 75 percent of the world's giant panda population.
As a hydraulic lift jerked into motion to hoist Tai Shan upward and place him in the belly of the giant plane, the panda turned again and looked back towards the crowd and Washington. Then the doors on the giant plane closed and the engines of the Panda Express roared into action.
Tai Shan and Mei Lan were nose-up shortly after noon, and Washington and Atlanta were left with the feeling of an empty nest.
-------------------------------------------------------------------------