Gigi Hadid

Gigi Hadid

Gigi Hadid remembers the 9/11 terrorist attacks like they were "yesterday".

The 21-year-old model vividly recalls sitting in school in a state of "shock and horror" when terrorists crashed hijacked planes into New York's twin towers in 2001 and has urged people to "never forget" the tragedy.

She tweeted: "The other night I watched the 9/11 doc. "Out of the Clear Blue Sky"

"May we never forget the people who lost their lives as INDIVIDUALS -- May we never forget the heroes who sacrificed their lives to respond

"Or the families that've been strong enough to pick up the pieces --

"I still remember sitting in my 1st grade classroom in shock and horror. Feels like yesterday. #NeverForget15years (sic)"

With the anniversary of the tragedy coming round last weekend, Gigi wasn't the only star to recall their vivid memories of the day.

Ashley Tisdale posted: "I was sick with the stomach flu the morning of, had the news on because my dad had gotten a call from family in NJ #NeverForget15years

"I'll never forget that morning, I'll never forget those we lost, and I'll never forget the heroes who rushed to help #NeverForget15years (sic)"

Kourtney Kardashian shared a picture of the New York skyline.

She tweeted alongside the picture: "I will #neverforget this day 15 years ago. Reflecting on the absence but also remembering the strength and courage.(sic)"

Her sister, Kim Kardashian West, also paid tribute to the victims of the tragedy.

She posted: "Life is so precious & I pray for everyone who was affected by this awful tragedy. #NeverForget911(sic)"

Meanwhile former Governor of California Arnold Schwarzenegger and 'Poker Face' singer Lady Gaga also posted their own tributes.

The 'Expendables' actor wrote: "Never forget the lives lost. Never forget the first responders who charged toward danger. Never forget our unity and resolve. #neverforget (sic)"

Gaga posted: "God Bless all the men and women who died in the attacks or fight to save lives during the Sept. 11 attacks #WeWillNeverForget #NewYorker (sic)"