On Saturday, the 20th anniversary of the tragic terrorist assault, there will be ceremonies at the 9/11 Memorial in New York.

Four al-Qaida militants hijacked four aircraft during the terrorist strikes on September 11, killing almost 3,000 people.

The World Trade Center’s north and south towers fell that terrible day after being struck by American Airlines Flight 11 and United Airlines Flight 175 respectively.

Another jet crashed in Pennsylvania when courageous passengers resisted the hijackers, while another crashed into the Pentagon.

We will never forget the tales from 9/11, whether they were from survivors, loved ones of the dead, firemen, police officers, or any of the other heroes who aided both on the ground and from the air.

In fact, when American Airlines Flight 11 and United Airlines Flight 175 crashed into the north and south buildings of the World Trade Center, some celebrities were supposed to be on the aircraft while others were intended to be in the Twin Towers.

Here are some of the famous people who were dangerously close to being on the that day’s crashed aircraft or in the wrecked buildings.

On the morning of 9/11, Michael Jackson was due to attend a meeting at the top of one of the sky-scraper.

According to one of his brothers, the King of Pop overslept that morning after he stayed up late speaking on the phone to his mother, Katherine, and his sister, Rebbie.

“Thankfully, none of us had had a clue that Michael was due at a meeting that morning at the top of one of the Twin Towers,” Jermaine Jackson wrote in his book, You Are Not Alone: Michael: Through a Brother’s Eyes.

“‘Mother, I’m okay, thanks to you,’ he told her. ‘You kept me up talking so late that I overslept and missed my appointment,’” Jermaine wrote.

Jackson died eight years later after he suffered a cardiac arrest brought on by a prescription pill overdose.

Mark Wahlberg

On the day of the attacks, actor Mark Wahlberg was scheduled to fly on American Airlines Flight 11 – the first plane that crashed into the World Trade Center.

Instead, he was invited to attend a film festival in Toronto, and decided to charter a jet with some of his friends.

Wahlberg stirred up quite a bit of controversy in later years by claiming that if he had been on that flight, he would have stopped the attacks from happening.

“If I was on that plane with my kids, it wouldn’t have went down like it did,” he told Men’s Journal.

“There would have been a lot of blood in that first-class cabin and then me saying, ‘OK, we’re going to land somewhere safely, don’t worry.’”

He subsequently apologised, admitting, “To speculate about such a situation is ridiculous, to begin with, and to suggest I would have done anything differently than the passengers on that plane was irresponsible.

“I deeply apologise to the families of the victims that my answer came off as insensitive, it was certainly not my intention.”

Like Mark Wahlberg, Seth MacFarlane was supposed to board American Airlines Flight 11. MacFarlane had been out drinking the night before, and had a history of missing flights. His travel agent also listed the flight time as being ten minutes later than it actually was.

“I was booked on that flight and I was drinking the night before and hung over and I missed the plane by about 10 minutes,” MacFarlane told the Mirror years later. “It was a very close call for me.”

After booking the next flight, MacFarlane said in a CNN interview, he then took a nap at the airport’s lounge, and woke up 45 minutes later amid the commotion of people learning the terrible news. Seeing the footage of his flight crashing into the North Tower, MacFarlane told an airport bartender he was supposed to be on that plane. The bartender gave him a shot.

While Gwyneth Paltrow wasn’t caught up in the tragedy herself, she was the saving grace for one office worker.

The Marvel star came across Lara Lundstrom Clarke in the morning, who was left starstruck over their chance meeting and took a moment to gather herself over the celeb spot – but was delayed enough to miss her train to work.

If they hadn’t had the encounter, she would have been on the 77th floor of the south tower when the plane crashed into it.

Speaking to Reuters of their meet, Paltrow said: ’It was an extraordinary story and all I could think about is all of the people who had experiences like that that day, but aren’t able to reach out because it wasn’t a recognisable person.

‘She saw it was me so she was able to get me a message, but I think a lot of fates were changed that day obviously and I am very humbly happy to be a part in her story.’

The Duchess of York, Sarah Ferguson, was filming an interview on Good Morning America on the morning of September 11th, 2001. She finished up the segment, and was on her way to her office on the 101st floor of the North Tower at 1 World Trade Center when she heard the news.

Sarah Ferguson was due to attend a meeting there that morning, but an interview with Matt Lauer at the nearby NBC studios ran late, saving the Duchess from attending the meeting.

None of the employees at her charity, Chances for Children, were killed.

Ferguson later spoke to Hello! Magazine about her “near-death experience.” “I take every minute as a blessing,” she said. “Because the minute you look too far forward, then you’re missing now. The minute you look back…you can’t go back.”

Surprisingly, a rag doll named Little Red, which was the charity’s mascot and sat on her desk, was discovered among the rubble.

Rob Lowe was on an American Airlines flight just 11 days before a plane taking the very same flight route crashed into the Pentagon. It turned out the hijackers were on board Lowe’s flight, practicing and preparing for their attack plan. “It was a dry run with the 9/11 hijackers surrounding me in the cabin, same crew,” Lowe told ABC.

The flight had been after he taped an episode of The West Wing and had been a normal journey so the actor was stunned to receive a notice in the mail that 9/11 plotter, Zacarias Moussaoui, wanted him to be part of the deposition at Moussaoui’s trial.

Turns out the actor had been sat next to Moussaoui during a test run on their flight.

Moussaoui wasn’t one of the actual hijackers on Sept. 11, but was later captured and sentenced to life for his role in planning the attacks.

“I flew with the 9/11 hijackers on the dry run, without realising. I was shooting The West Wing in DC at the time, and I always took the flight that leaves Dulles to Los Angeles that they eventually put into the Pentagon,” he said.

“I made the flight a lot and I didn’t think anything of it. I got on the flight and it was packed, small plane.

“Looked around the cabin, don’t remember anything in particular, nobody looked scary, nobody looked like a terrorist. It looked like an absolutely normal flight.”

Singer Patti Austin was supposed to be on the United Flight 93, which was taken over by passengers who managed to stop the hijackers plans but still died.

However, her mother had a stroke in San Francisco, so she updated her itinerary.

It turned out that terrorists on the jazz legend’s original flight were targeting the Capitol building in Washington, D.C. Passengers aboard the plane helped stop the attack and the plane crashed into a field in Pennsylvania.

“I felt that my life had been saved for some specific reason,” Austin told NBC. “I have yet to figure that out, but I do a lot of charity work now, which I was doing before, but I do a lot more.”

Austin recalled how her manager broke the news of her near miss. “Remember, you were supposed to go to the second day of the show, and you had get out first thing in the morning, and that was the only thing that left early enough in the morning to get you back into San Francisco in time to be with your mom,’ and I completely lost it,” says Austin.

Robert De Niro was one of the many stars who watched the horrors unfold straight from their windows.

The native New Yorker explained: ‘I left a meeting right after they hit the World Trade Center. I went to my apartment, which looks south, and I watched it out my window. I could see the line of fire across the North Tower. I had my binoculars and a video camera – though I didn’t want to video it.

‘I saw a few people jump. Then I saw the South Tower go. It was so unreal, I had to confirm it by immediately looking at the television screen. CNN was on. That was the only way to make it real. Like my son said: “It was like watching the moon fall.”‘

Greer Epstein said she rarely ever left her desk at work, but on the morning of September 11th, one of her coworkers at Morgan Stanley managed to talk her into taking a cigarette break at around 8:40am. As she stepped out to have her smoke, she saw people looking up at the sky. She watched as debris rained down from the towers, and wondered what exactly was happening. As she stood there watching, the second plane flew into the South Tower, where her office was.

“I never took a break before noon,” Epstein said. “It was something that happened that day. And thank God for it. I was safely out of the building when the plane hit. A fireball went through my office. Had I been sitting there, who knows what would’ve been?”

Steve Buscemi had worked as a firefighter in the Eighties, and made his way to the scenes to help rescue efforts for five days.

He worked 12-hour shifts for several days in search of survivors and said at the time: ‘It was a privilege to be able to do it. It was great to connect with the firehouse I used to work with and with some of the guys I worked alongside.

‘And it was enormously helpful for me because while I was working, I didn’t really think about it as much, feel it as much.’

In a recent interview with Mark Maron, he stated: ‘I was privileged enough to have access to the site and be in the thick of it, and just experience the humanity of what was going on there.’

When the podcast host asked if he had experienced any long-term health issues or PTSD, Buscemi replied: ‘I haven’t experienced any health issues, and I get myself checked out, but definitely…. Post traumatic stress? Absolutely.

‘I was only there for like five days, but when I stopped going and tried to just live my life again, it was really, really hard. I was depressed, I was anxious, I couldn’t make a simple decision. All those things. It’s still with me. There are times when I talk about 9/11 and I’m right back there. I start to get choked up and I realise, ah, this is still a big part of me.’

Gabourey Sidibe was supposed to attend class across the street from the World Trade Center on Sept. 11, 2001. Fortunately, she overslept and she only learned of the attacks when she turned on her television. It turns out that Sidibe may have been seriously injured or even died had she attended class that morning.

“Later that day, one of the towers fell on the school building that I had class in, and people lost their lives. [Borough of Manhattan Community College] shut down for a month because the school became a make-shift space for police, firefighters and EMTs,” the Precious star told the New York Daily News.

Once classes resumed, Sidibe recalled smelling soot and ash. In the entryway of the school hangs framed photos of those who died on campus.

Chef Michael Lomonaco’s poor eyesight saved him that day.

Known for overseeing three popular Manhattan restaurants, including the famous Windows of the World restaurant on the 106th and 107th floors of 1 World Trade, he had an appointment to get his glasses repaired at noon that day in the lobby.