Carolyn Bessette died in a plane crash alongside her husband John F. Kennedy Jr. and sister Lauren on July 16, 1999

Kelly Klein is honoring her late friend Carolyn Bessette on the 21st anniversary of her death.

On Thursday, Klein, photographer, artist and ex-wife to designer Calvin Klein, shared an old photo of her and Bessette traveling, adding the hashtags #throwbackthursday, #berlinwall and #vintageshopping. The pair first became friends when Bessette started working as a public relations executive at Klein's then-husband’s fashion brand.

Bessette died on July 16, 1999 when the plane her husband, John F. Kennedy Jr., was piloting crashed into the Atlantic Ocean off of Martha's Vineyard. Bessette's sister Lauren were also on the flight during the crash, which killed all three.

JFK JR. and Carolyn
From left: John F. Kennedy Jr. and Carolyn Bessette Kennedy in 1999
| Credit: Justin Ide/Getty

“She was so warm and funny,” Rose Marie Terenzio, who was JFK Jr.’s executive assistant, told PEOPLE of Bessette in January of this year, marking the month Bessette would have turned 54.

“Our birthdays are close together, so we would always do something alone together in between her birthday and mine,” Terenzio said. “She always made it so special picking a place we’d never been before or somewhere we loved. She always bought me something nice when we would shop. She would insist.”

Bessette was “quite a lovable person,” close friend Carole Radziwill, the widow of Kennedy cousin Anthony Radziwill, also previously told PEOPLE. “She was clever, she was naughty and she had that balance of being able to be really serious and deep yet funny.”

John F. Kennedy Jr. And Carolyn Bessette Kennedy
From left: Carolyn Bessette Kennedy and John F. Kennedy Jr. in 1997
| Credit: Dave Allocca/DMI/The LIFE Picture Collection/Getty

She grew up in Greenwich, Connecticut, and graduated from Boston University, where she began dabbling in modeling and fashion.

Bessette later moved to New York City for her job as a publicist at Calvin Klein and was called an “amazing symbol of American style” by Harper’s Bazaar Editor-in-Chief Liz Tilberis after she gained a mainstream following when her relationship with JFK Jr. went public in the mid ’90s.

Credit: Jon Naso/NY Daily News Archive/Getty Images

Bessette and JFK Jr. married in a secret ceremony on an isolated island off the coast of Georgia in September 1996, three years before they died in the crash.

“John and Carolyn were magic together,” JFK Jr.’s friend Gustavo Paredes told PEOPLE in 2014. “She had an earthiness and a gentle fierceness. Together, they were whole.”

“John and Carolyn were wonderful people. They fell in love, they had a stunning, dreamlike wedding,” another friend, Sasha Chermayeff, later added. “I don’t know what would have come to pass had they not night died that night 20 summers ago — and no one does.”