The US-born giant panda Bei Bei has left his home at Washington's National Zoo for China.
Bei Bei will travel on a specially equipped flight from Washington to Chengdu, accompanied by his keeper and a veterinarian.
The giant panda turned four years - the age when all pandas born outside return to China under their breeding agreements.
"Today is bittersweet. We've cared for Bei Bei, and along with millions, watched him grow into a true ambassador for his species," said zoo director Steve Monfort.
"We look forward to continuing our 47-year giant panda conservation program and collaboration with Chinese colleagues to study, care for and help save the giant panda and its native habitat."
Zoo officials said they had prepared a special stash of treats for him: 30 kilos of bamboo, two pounds of apples and pears, two pounds of cooked sweet potatoes, two bags of biscuits and water.
India's youth protests end as Modi's education minister quits
Ukraine kills 11 in tourist camp, Russia says
At least 35 killed in bus collision in Syria
Wildfires force evacuations outside Bordeaux as wind stokes Spanish blazes
Venezuela quake recovery will take years, says Red Cross
