September 11, 2001, wasn't just a single event. It was a rapid-fire sequence of catastrophes that essentially broke the American psyche for a generation. Most people remember the smoke. They remember the towers falling. But if you actually dig into the timeline of what attacks happened on 9/11, it’s a terrifyingly coordinated strike involving four commercial airliners, nineteen hijackers, and a series of failures that still seem impossible decades later.
It started like any other Tuesday. Clear blue skies. Millions of people were just getting their first coffee when the world shifted.
The First Strike: American Airlines Flight 11
The first plane hit the North Tower of the World Trade Center at 8:46 a.m. This was American Airlines Flight 11. It had taken off from Boston, headed for Los Angeles, carrying 81 passengers and 11 crew members. When it slammed into the tower between the 93rd and 99th floors, most people watching on TV—and even the first responders on the ground—thought it was a freak accident. Maybe a small private plane lost its way?
That illusion lasted exactly seventeen minutes.
Inside that plane, things had turned dark long before impact. We know from phone calls made by flight attendants Betty Ong and Amy Sweeney that the hijackers had used mace and knives to take the cockpit. They were calm. They were methodical. They had trained for this in flight schools across the U.S. south.
9:03 A.M.: The Moment Everything Changed
United Airlines Flight 175 hit the South Tower. This is the shot everyone has burned into their brain. Because the news cameras were already pointed at the North Tower, millions watched the second plane bank sharply and disappear into the steel and glass of the second skyscraper.
This was the pivot point.
Suddenly, it wasn't an accident. It was an attack. The South Tower was struck between floors 77 and 85. Ironically, the second tower hit was the first to fall. It stood for 56 minutes after impact. The North Tower, hit first, stood for 102 minutes.
The physics of the collapse are often misunderstood. It wasn't just the impact; it was the jet fuel. Thousands of gallons of fuel poured down elevator shafts, weakening the steel floor trusses. Once the top section of the building started to drop, the weight was simply too much for the floors below to catch. It’s called a progressive collapse.
The Pentagon: The Attack People Often Forget
While New York was burning, the third plane was still in the air. American Airlines Flight 77 had been hijacked after departing Dulles International Airport. At 9:37 a.m., it crashed into the western side of the Pentagon in Arlington, Virginia.
125 people in the building died. 64 people on the plane died.
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The Pentagon is a massive concrete fortress, but a Boeing 757 traveling at over 500 miles per hour is essentially a guided missile. The damage was catastrophic. A whole section of the building collapsed. It’s wild to think that the nerve center of the U.S. military was breached so easily, but the hijackers had found a "blind spot" in the airspace.
The Flight That Fought Back: United 93
Then there’s the fourth plane. United Airlines Flight 93. This one is different because the passengers knew what was happening. Because the flight was delayed on the tarmac for 42 minutes, passengers were able to make phone calls to loved ones. They found out about the World Trade Center. They realized their plane wasn't being held for ransom—it was being used as a weapon.
Todd Beamer. Sandy Bradshaw. Mark Bingham. These names became legendary.
They decided to storm the cockpit. We have the cockpit voice recorder data. You can hear the struggle, the shouting, the sound of a food cart being used as a battering ram. The hijackers, realizing they wouldn't reach their target (likely the U.S. Capitol or the White House), flipped the plane upside down and dove into a field in Shanksville, Pennsylvania.
It crashed at 10:03 a.m. No one survived, but they likely saved hundreds of lives in D.C.
The Aftermath and the Scale of Loss
The numbers are staggering. 2,977 victims. That doesn't include the 19 hijackers. Most of those deaths occurred at the World Trade Center, including 343 firefighters and 60 police officers who ran into the buildings while everyone else was running out.
The cleanup took years. The health effects—cancers from the toxic dust—are still killing people today. In fact, more first responders have now died from 9/11-related illnesses than died on the day of the attacks.
What Most People Get Wrong About the Day
There’s this idea that the government was totally oblivious. It’s more complicated. The "wall" between the CIA and FBI prevented them from sharing information that could have flagged some of the hijackers.
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Another misconception? That the buildings fell because the steel melted. Steel doesn't have to melt to fail; it just has to lose about 50% of its structural integrity, which happens at around 1,100 degrees Fahrenheit. Jet fuel burns at a temperature high enough to do that easily.
Key Takeaways for Understanding the 9/11 Timeline
If you're trying to wrap your head around what attacks happened on 9/11, you have to look at the timeline as a series of cascading failures and incredible acts of bravery.
- 8:46 AM: North Tower hit (Flight 11).
- 9:03 AM: South Tower hit (Flight 175).
- 9:37 AM: Pentagon hit (Flight 77).
- 9:59 AM: South Tower collapses.
- 10:03 AM: United 93 crashes in Pennsylvania.
- 10:28 AM: North Tower collapses.
The day changed everything from how we board a plane to how we view privacy. It sparked two wars and shifted the global geopolitical landscape for decades.
To truly grasp the impact, look into the 9/11 Commission Report. It’s a long read, but it’s the most definitive account of how the security gaps were exploited. You can also visit the 9/11 Memorial & Museum website to hear the oral histories of survivors; hearing the voices of those who were actually there is a lot more powerful than just reading a list of facts. If you're in New York, the memorial at Ground Zero is essential. Standing in the footprint of those towers gives you a sense of scale that no video ever will. Keep researching the long-term health effects on the survivors—the story didn't end in 2001.