Prince Harry, Duchess Meghan, Kate Hudson and more remember Sept. 11, 20 years later

Celebrities are remembering the Sept. 11, 2001, attacks by sharing memories and comforting words on social media. 

It was 20 years ago when 19 al-Qaida hijackers took over four commercial airplanes in a plot orchestrated by Osama bin Laden.

Many people gathered to honor the dead Saturday, including President Joe Biden. Ceremonies were held in New York City, at the Pentagon and outside Shanksville, Pennsylvania — the sites where planes crashed during the attacks. 

The Duke and Duchess of Sussex paid their respects to those who died in the attacks with a tribute on their Archewell website. The website's page was made over with a list of the nearly 3,000 victims of the attacks underneath the words "In Memoriam" on a black background.  

Queen Elizabeth II also wrote a statement to Biden offering  her "thoughts and prayers."

"My visit to the site of the World Trade Center in 2010 is held fast in my memory." she wrote in the statement. "It reminds me that as we honour those from many nations, faiths, and backgrounds who lost their lives, we also pay tribute to the resilience and determination of the communities who joined together to rebuild." 

Other celebrities like Kate Hudson used social media to give tributes on Saturday. Hudson included a photo of lights being shone from Ground Zero with a heartfelt caption. 

"It’s hard to believe it’s been so long since this devastating event in our history. Being in the city right now brings back so many memories," Hudson wrote. "Everyone remembers where they were: when they got the call or seeing it on the news. Those of us who were living in New York saw a different city. A city in mourning yet together." 

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Nearly 3,000 lives were lost in the attacks and stars like Reese Witherspoon, Wale and Mariah Carey used social media to commemorate the tragic day.

Witherspoon tweeted: "My prayers go out to all the families that lost their loves ones on this day 20 years ago. We will #neverforget. Forever in our hearts." 

Rapper Wale tweeted while catching a flight Saturday he still feels the "pain and trauma" of what Sept. 11 means. 

"Flying to DC right now . On THIS day .. the pain and trauma still very much present at the airport and on this plane so many years later … we will #neverforget," he wrote. 

Carey described feeling "shock and anguish" 20 years ago.  

"Vivid images of the skyline I grew up loving so much, suddenly changed forever," she wrote. "Still astonished by how many innocent people were lost in an instant, gone forever but never to be forgotten." 

"Respect" star Jennifer Hudson wrote: "It’s been 20 years and we will never forget. Join me in praying for the loved ones of all those we lost." 

Former "Grey's Anatomy" actor Sara Ramírez tweeted that meditating this morning helped calm her "uneasy" feelings about what today marked. 

"Woke up today feeling all kinds of uneasy. Sometimes feeling into what our bodies are communicating takes time and real patience," Sara Ramírez tweeted. "Meditation helped. Sending warmth and tenderness to those who are open to receiving. #September11."

Contributing: Ryan W. Miller