Bao Bao licks a hot-pink plastic crate on the panda’s last day at the National Zoo. (Amanda Voisard/For the Washington Post)

To fall in love with a panda, according to those who know, you have to get to know it as an individual.

“You don’t just look at them and say, ‘Okay, I’ve seen a panda,’ ” said Elspeth Grindlay, a diminutive woman who arrived at the National Zoo at 8 a.m. Monday in a panda T-shirt, with panda pendants around her neck. Rather, it is through hours of watching it lumber about, chew on bamboo and expose its furry tummy that you come to understand its spirit.

That is why Grindlay has flown to Washington from Ayr, Scotland, five times in the past year alone, and why this visit was the most bittersweet. Bao Bao, the panda she and countless others fell in love with when she was born at the National Zoo 3½ years ago, is leaving. At 1:30 Tuesday, the bear will depart on a special flight from Dulles International Airport to Chengdu, China.

This was fans’ opportunity to say goodbye. Like pilgrims, they proceeded down the Asia Trail, bypassing the sloth bear, the clouded leopard and the Asian small-clawed otter.

Many had driven from afar to find the surrounding roads jammed with cars and the wait for a parking space more than an hour (to keep them going, the Connecticut Avenue Starbucks concocted a Pandaccino — a double-chocolate Frappuccino with white mocha, “layered with whip cream and love”).

Most of the world’s giant pandas are on loan from China, and cubs born abroad are sent to the Chinese breeding program before they turn 4. Although the National Zoo has had pandas since 1972, Bao Bao is only the second surviving one born there; her older brother Tai Shan moved to China in 2010.

Vicky Zhang, a Rockville resident from China, brought her two U.S.-born children to see her off. “We want the kids to know the panda is from China, and hopefully someday we can go back to see her in China,” she said. “If you mention pandas, everyone knows it comes from China, and we are proud of that.”

On her 16-hour nonstop flight, courtesy of FedEx, Bao Bao will be accompanied by a veterinarian as well as a panda keeper who held her when she was a day-old cub.

“The keepers who’ve been with her every day are going to miss her, but she’s going to be doing a positive thing, hopefully going on to breed new pandas and release some of them into the wild,” said Erin Kendrick, a clinical nutritionist at the zoo.

Bao Bao gets a bear-size luggage allotment, and she’s allowed to carry plants and liquids. Her special “suitcase” will contain 50 pounds of bamboo, two pounds of cooked sweet potatoes, two pounds of apples, 10 gallons of water, and honey water and sugar cane.

At 10 a.m., visitors let out a collective “Awww” as Bao Bao received a farewell ice cake in the shape of a Chinese pagoda, made of frozen apple juice, red “leafeater” biscuits and two kinds of bamboo.

Adults and children crowded around a table to write postcards to the departing starlet and to her new keepers in China. Some added Chinese characters, to represent the journey to her new home, or the District’s stars and stripes logo, to remind her of her old one.

(Claritza Jimenez,Dani Player/The Washington Post)

Dear Bao Bao, I will miss you a ton. Why did you have to go? With hugs, kisses, and a lot of love, Beril Gunduzhan

“Maybe she will miss us, too,” said Beril, 8, of Bethesda, who was there with her mother and older sister.

Why are pandas so adored? “That expression,” said Blaine D’Amico of Arlington. “They seem more friendly and human, even though they are bears. . . . And they’re vegetarians. I mean, a vegetarian bear.”

To Melinda Maldonado, an Arlington resident originally from Austin, the love is spiritual.

“I think that when you see an animal with a pattern like that — a giraffe or a panda — you realize there’s a God, there’s the entity that created all this,” she said. “It also reminds us that we need to take care of our planet. It’s not just about materialism and greed and one-upping each other.”

Although Bao Bao has been receiving ice cakes and extra visitors these past days, the panda probably didn’t know it was her last full day in her birth country, and she may not feel very nostalgic once she figures it out. She has lived in her own enclosure since 2015 — pandas are solitary in the wild — so she’s unlikely to miss her parents, Mei Xiang and Tian Tian, or her little brother Bei Bei.

Perhaps it was just the unseasonably warm day that inspired her to put on one last show, to gambol around her enclosure, to bat at a burlap bag and to hug a special cardboard suitcase presented to her at 1:30.

She wrapped her arms around a hot-pink plastic crate and licked it. That was when Leslie Johnson lost it.

“I gave her that crate,” said the Fairfax resident and regular Bao Bao visitor, dabbing at tears.

“I’m sad but happy,” she said. “It’s like sending a kid off to college. . . . What we all want for her is to perpetuate the species and have beautiful little cubbies. But it’s hard to watch her go.”