Carole Radziwill was the daughter-in-law of Lee Radizwill, the sister of Jackie Kennedy Onassis. Carole married Lee's son Anthony in 1994 after the two worked as producers for ABC News. Following Anthony's death due to sarcoma cancer in 1999, Carole continued her journalism career and in 2011 joined the cast of The Real Housewives of New York City.

The 55-year-old was featured in the main cast for seasons 5-10. She announced her departure in July of 2018, along with her plans to return to journalism. Carole is currently working on a memoir picking up where her 2005 book What Remains: A Memoir of Fate, Friendship and Love left off through Real Housewives of New York City and today.

Here, in this DailyMail.com exclusive essay, she writes about the deaths of her closest friends - her late husband's cousin John Kennedy, his wife Carolyn and her older sister Lauren Bessette on the 20th anniversary of the tragic plane crash. She is featured in a A&E documentary on the tragic Kennedy prince airing Tuesday, July 16 at 9 pm EST

I wrote a book several years ago, because I experienced personal trauma in my life. I had pain, and I wrote it down. I started my story on July 16, 1999, because there was no other place to begin.

On that day, just before midnight, a small plane went into the ocean and three people died. They were all close to me. At the time, my lifeline. My husband's cousin, John Kennedy; his wife, Carolyn, my closest friend, and her older sister Lauren Bessette. I lost everything that night, I wasn't the only one.

We all lost something. It was personal for me, and for their friends and family, but it was also bigger.

1999 was the end of an era. The end of a century. It was the end of an innocence we didn't even know we had. A time before tweets, posts and status updates. Before Instagram influencers, before everyone carried a 24/7 never-ending font of information in their hands.

Before the dubious fame and spoils of non-stop reality TV, there was 1999 — it was before the world was prepared to crash from Y2K computer glitches. It was before John and Carolyn died.

Real Housewife Carole Radziwill, the daughter-in-law of Lee Radizwill, the sister of Jackie Kennedy, married Lee's son Anthony Radziwill in 1994 The 55-year-old was close friends with Anthony's cousin John Kennedy Jr and his wife Carolyn, who tragically died in a plane crash on July 16, 1999 The journalist reflects on losing them so young, writing: 'It was a simple accident. A single engine plane fell out of the sky into the ocean'. Pictured: Carole with her late husband Anthony Radziwill (left) and John Kennedy Jr (right)

The 55-year-old writes: 'It was a simple accident. A single engine plane fell out of the sky into the ocean. The pilot was my husband's cousin, John Kennedy, his passengers were his wife Carolyn, and her sister, Lauren. Three young, bright, people with promising futures. Less than a month later, my husband Anthony died, too.' Pictured: Anthony Radziwill with Carolyn Bessette-Kennedy on her wedding night in September of 1996

'The pain of losing them, once so acute it was unbearable, has eroded over time. Somewhere along the way their deaths became a thing I am able to live with. They inhabit my memory as their forever 30-something selves, while I turned 40 and then 50 and now 55. Nothing has changed and everything has,' Carole writes

It's hard not to think of how we've changed as a culture in 20 years — our political landscape, yes, but also personally. 1999 was pre-9/11, pre-governing by tweet, pre-Kardashians, pre-Tinder, pre-kale, pre-woke, pre-Netflix and chill.

Prince made the year iconic in a hit single he wrote in 1982, his own sly wink at doom. The Sopranos debuted, Justin and Britney got together and Carrie Bradshaw and Big broke up, again. Bill Clinton was acquitted that year, and most of the country liked him. The Dow was up, crime was down. Jon Stewart debuted as host of The Daily Show, and after 18 nominations Susan Lucci won her EMMY.

Two boys who shot up their high school dominated the news that spring but from the early morning hours of July 17th the news was one story only, around the clock. Not a political scandal, or crime spree. A plane that didn't land at a small airport on Cape Cod.

It was a simple accident. A single engine plane fell out of the sky into the ocean. The pilot was my husband's cousin, John Kennedy, his passengers were his wife Carolyn, and her sister, Lauren. Three young, bright, people with promising futures. Less than a month later, my husband Anthony died, too.

All four of them gone when they were just beginning to form lives. At an age when people lock in careers or start families, find their faith, their purpose, their bliss. Gone when all those life markers were still sorting out.

The pain of losing them, once so acute it was unbearable, has eroded over time. Somewhere along the way their deaths became a thing I am able to live with. They inhabit my memory as their forever 30-something selves, while I turned 40 and then 50 and now 55.

Nothing has changed and everything has. I left a career to start a new one, and then another. I found new friends, lost others, moved across the country, across the ocean, had crushes, love, and petty feuds. They still hold court in a nostalgic back room where they haven't seen any of it. No milestones, no soft jokes about the inevitable slights of age.

'Lives, and promise, cut short. All of them in three cruel weeks. Carolyn Bessette Kennedy, John F. Kennedy, Jr., Lauren Bessette. And my husband, Anthony Stanislas Albert Radziwill. For all the time I'd had to brace myself, prepare for it, Anthony's death, too, still seemed so abrupt and unfair, just like the others. Because ... we just weren't done.' Pictured: Carole and John Jr at Carole's wedding to Anthony in 1994

'September 21, three years earlier, was similar. It was a Saturday at the Greyfield Inn on Cumberland Island, a secluded spot off the coast of Georgia. There were wild horses and wildflowers, it was untouched and bucolic. That night there was a wedding — one of the best-kept secrets of modern time.' Pictured: Carolyn and John Jr on the night of their wedding

'But we all pulled off the coup of the century that weekend. John Kennedy Jr., the most famous man in the world got married on a pastoral remote island off the coast of Georgia and no one knew. Not a paparazzi in sight,' Carole writes

They are trapped in 1999, like a fossil under hardened amber. It's difficult to know what life would be like today, if they were here. I only know the plans we made that didn't happen. When someone dies young you mourn what was, and you mourn what could have been.

When I think of 1999, I think of George magazine — John's nascent publishing career, his smart, cutting-edge fusion of serious political coverage with pop culture, and the loyal staff that held it together.

I think about the HBO documentary Anthony produced about Lenny Bruce that received an Oscar nod that year. He was passionate about his work, he was respected for it, and devoted to the talent he worked with.

I think of my closest friend, Carolyn, who had hope even as Anthony was losing his fight with cancer. We were making plans before she died — for Anthony's 40th birthday a few weeks away, for my sister-in-law, Tina's, bridal shower.

For the road trip we planned to take in a vintage gold 1964 Mustang we saw for sale, and fell in love with, that summer on Martha's Vineyard. There was so much life still to come.

The four of us had planned a trip to Skorpios that winter, a nostalgic romp through the memory lanes of Anthony and John's youth. We had hope.

Carolyn was the glue who kept people together. Specifically, that summer, the four of us in a difficult time. There was hope that George magazine would turn around. Hope that being together at the beach, after a family wedding in Hyannis, would correct a few errant curveballs. We'd all breathe, find strength enough in one day to be able to handle the next.

Carole writes that her mother-in-law Lee Radziwill 'gave Anthony and me an unforgettable wedding, with a dinner and reception under a Christian Tortu-designed tent that she filled with family, friends and affection'

Carole said after her husband Anthony died of sarcoma cancer in 1999, she and her mother-in-law Lee Radziwill 'clung together in grief'. Pictured: Carole on her wedding day with Anthony and Lee in 1994

Pictured: John Jr and Carole's late husband Anthony on John's wedding day in 1996

When I married my husband in 1994, he had a death sentence. He was determined to overturn it, but I'd done the research and knew his chances were slim.

We spent ten years together, the last five of them in and out of hospitals, and in again. Carolyn made every day of those five years about living, not dying. She made what might have otherwise been a hopelessly grim existence, fun.

These were family, my friends, the people closest to me. But they also meant something to the country, and the world. John balanced the weight and hopes of a new century's dreams.

Carolyn launched a thousand style knockoffs, with her casual chic grace. Like Princess Diana and her mother-in-law before her, she was easy on the camera and before she died, the most sought-out photograph in the world. She was beautiful, yes.

But I've yet to hear a description of a truly beautiful woman, that wasn't intentionally or not, a characterization of her inner good, and the way it shined onto others.

Then, July 16, 1999. The day had all the earmarks of innocence. A blue sky, a warm breeze, the sounds of lawnmowers humming through open windows. It was a Friday, a day for plans. How could you possibly be prepared for a plane to fall from the sky on a bright blue summer day like that?

September 21, three years earlier, was similar. It was a Saturday at the Greyfield Inn on Cumberland Island, a secluded spot off the coast of Georgia. There were wild horses and wildflowers, it was untouched and bucolic.

The former RHONY star described the close bond between Anthony and John Jr, writing: 'They were the odd couple. John scattered and impulsive; Anthony methodical and sensible. They couldn't live without each other, and they didn't.' Pictured: The two men on vacation

'Like Princess Diana and her mother-in-law before her, she was easy on the camera and before she died, the most sought-out photograph in the world. She was beautiful, yes. But I've yet to hear a description of a truly beautiful woman, that wasn't intentionally or not, a characterization of her inner good, and the way it shined onto others,' Carole writes. Pictured: Carolyn posing on back of a car with a friend

That night there was a wedding — one of the best-kept secrets of modern time. Guests had to present a special Indian nickel upon landing on the island or they were quickly escorted off. It was the most famous wedding of the year, the decade. And no one but the thirty-two close friends and family who arrived, knew.

Lauren, Carolyn and I spent hours cutting the stems off of dozens of big Alaskan white roses that afternoon, arranging them in silver buckets for the dinner tables. John came by at one point, just to hang out.

It was that kind of carefree day. We were all happy to be there, we had a wedding that night. John felt obligated to weigh in, though, on the buckets. 'Three per table,' he said. It was a wild guess. He was flirting with his just hours-away wife. He shrugged at our eye-roll, she giggled at his charm. He said, 'Hey, I know what I'm doing. I got this.'

He didn't. That was the sweet running joke. Four hours later, all of us overdue at the small chapel and waiting on him, he ran panicked to our room.

'I can't find my shirt. Anthony!' He was accusing. 'Where is it? What'd you do?'

It was their childhood summed up in five frantic minutes, three decades of hi-jinx and pranks between two men with an unshakeable bond.

Anthony didn't hide John's shirt. John didn't know where it was. Anthony found the shirt. They were the odd couple. John scattered and impulsive; Anthony methodical and sensible. They couldn't live without each other, and they didn't.

'Frozen in mid-conversation, we had the luxury, the last time we spoke, of talking about what we might have for dinner Sunday. It was a quick call. John was preparing to take off from a small private airport. Anthony and I would see them, in their house on the Vineyard where we were staying, in 48 hours. The plan, for July 18, was grilled steaks and peach pie'

John F. Kennedy Jr gives his wife Carolyn Bessette Kennedy a kiss on the cheek during the annual White House Correspondents dinner on May 1, 1999 - just a few months before they died

But we all pulled off the coup of the century that weekend. John Kennedy Jr., the most famous man in the world got married on a pastoral remote island off the coast of Georgia and no one knew. Not a paparazzi in sight.

Months later Carolyn and I were on the couch at their apartment on North Moore Street. Anthony was working late that night. John was away on a business trip. It was a peaceful moment.

Carole is currently working on a memoir picking up where her 2005 book What Remains: A Memoir of Fate, Friendship and Love left off through Real Housewives of New York City and today

We ordered cheeseburgers from Bubby's, the diner on the corner, and looked through their wedding photos, loose in a box. 'That was crazy,' I said. 'To try to pull it off, then to do it. I honestly expected photographers on the beach and in the bushes.' Carolyn was proud of that. It was at the time, unbelievable.

'You just have to know who to trust.' She said. 'Know who your friends are.'

She did. She knew. That weekend was rare for its complete and personal intimacy. Carolyn knew that, it's what she wanted. We had it.

'But they got me back,' she joked — a subtle reference to the packs of photographers who had been trailing her non-stop since. 'Maybe I should've just played along, let them have the wedding.'

Frozen in mid-conversation, we had the luxury, the last time we spoke, of talking about what we might have for dinner Sunday. It was a quick call. John was preparing to take off from a small private airport.

Anthony and I would see them, in their house on the Vineyard where we were staying, in 48 hours. The plan, for July 18, was grilled steaks and peach pie.

Lives, and promise, cut short. All of them in three cruel weeks. Carolyn Bessette Kennedy, John F. Kennedy, Jr., Lauren Bessette. And my husband, Anthony Stanislas Albert Radziwill.

For all the time I'd had to brace myself, prepare for it, Anthony's death, too, still seemed so abrupt and unfair, just like the others. Because ... we just weren't done.