Zoo Atlanta bid farewell to its four giant pandas who left on a FedEx plane to China Saturday morning.

The pandas’ departure marks the end of a 25-year deal with the Chinese Association of Zoological Gardens and Chengdu Research Base of Giant Panda Breeding, where the pandas will begin the next chapter of their lives.

Three Zoo Atlanta team members are accompanying the pandas to ensure safety and comfort during their nearly 20-hour flight, according to the zoo. The pandas also will be traveling with more than 300 pounds of bamboo, about 10 pounds of fresh produce and six gallons of water.

Pandas Lun Lun and Yang Yang arrived at Zoo Atlanta as 2-year-old cubs in 1999 and bred seven cubs, five of whom are already back in China. Their 8-year-old twins Ya Lun and Xi Lun are traveling with them to Chengdu.

The zoo held a special “Panda-Palooza” farewell party Saturday with over 9,000 people in attendance.

The departure of the pandas comes as zoos across the United States, including San Diego, Memphis and Washington, D.C., have returned pandas to China in recent years. Yun Chuan and Xin Bao were the first new pandas to enter the U.S. in 21 years.