Kate Middleton and Prince William 'Delighted to Be Back in the U.S.' as They Touch Down in Boston

Chris Jackson/Getty Kate Middleton and Prince William

Kate Middleton and Prince William have landed in Boston!

The Prince and Princess of Wales, both 40, arrived in the United States on Wednesday afternoon for their three-day trip, where they'll spend time in the Boston area. The visit will culminate with William's second annual Earthshot Prize Awards ceremony on Friday.

The couple, who arrived by commercial flight at Boston Logan Airport, was greeted by Governor Charlie Baker, Lauren Baker, First Lady of Massachusetts and Lt. Gov. Karyn Polito.

Upon their arrival, William released a personal statement about their visit to America and paid tribute to his late grandmother Queen Elizabeth.

"Catherine and I are delighted to be back in the United States and are extremely grateful to Governor Baker and The First Lady of Massachusetts for their warm welcome into Boston," he said.

Chris Jackson/Getty Prince William and Kate Middleton

"On this, our first overseas visit since the death of my grandmother, I would like to thank the people of Massachusetts and particularly of Boston for their many tributes paid to the late Queen," he continued. "She remembered her 1976 bicentennial visit with great fondness."

Chris Jackson/Getty Prince William and Kate Middleton

"My grandmother was one of life's optimists. And so am I," he said. "That is why last year we launched the Earthshot Prize with the ambition to create a truly global platform to inspire hope and urgent optimism as we look to save the future of our planet.

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"To the people of Boston, thank you. I'm so grateful to you for allowing us to host the second year of the Earthshot Prize in your great city. Catherine and I can't wait to meet many of you in the days ahead."

The royal couple last came to the U.S. in 2014 for a visit to New York City. They also toured Los Angeles in 2011, their first joint trip to America after getting married in April of that year.

OHN TLUMACKI/POOL/AFP via Getty Prince William and Kate Middleton

"This is a huge moment for the Prince and Princess — it's their first visit to the U.S. since 2014, and they're very excited to be here," a spokesperson for the couple says.

"It's fair to say, having spoken to them yesterday following the coverage here in the U.S., that the Prince and Princess were really struck by the warm response of the American people to the news of their trip this week," the spokesperson continues. "And they're really looking forward to meeting communities across Boston over the next few days and trying to meet as many folks as possible."

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While the Earthshot Prize is the ultimate reason for their visit, the couple also sees it as an opportunity to "fact-find" about some of the causes and interests close to their hearts. "Some of the things we are focused on right now is supporting some of the most hard-pressed communities up and down the U.K. and we will continue to do that in Boston," says the source.

Prince William and Princess Kate's trip will start with a welcome at Boston City Hall, where Mayor Michelle Wu and Ambassador Caroline Kennedy will help the couple start the countdown to the Earthshot Prize ceremony by lighting up city landmarks in green.

On Thursday, the royals will see the work that local organizations in Boston are doing to create a more sustainable world, and they'll learn about some of the innovative technologies being utilized at Greentown Labs in Somerville.

Alberto Pezzali - WPA Pool / Getty Prince William and Kate Middleton

Later on Thursday, Prince William and Kate will hear about the efforts of Roca, a non-profit organization that works to create a cohesive approach to save and help change the journey of the lives of high-risk young people.

Princess Kate will make a solo visit to the Center on the Developing Child at Harvard University on Friday to learn some of the best practices that can be taken back to her own Royal Foundation and The Centre for Early Childhood as she builds her pioneering work in the area. Meanwhile, Prince William will make a solo outing of his own to tour the John F. Kennedy Presidential Library and Museum. President John F. Kennedy's Moonshot — which challenged America to put a man on the moon — is the key inspiration behind the Earthshot Prize.

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"The prize has become the Prince's Super Bowl moment of the year, and he looks forward to continuing to use the platform each year to shine a light on some of the most impactful projects doing amazing things around the world to save our planet's future," the source says.