9/11 Conspiracy Theories: Facts And Myths About What Happened On September 11

The deadliest terrorist attack on the U.S. soil took place on Sept. 11, 2001, when a series of coordinated attacks killed nearly 3,000 people and left more than 6,000 people injured.

On Monday, thousands of 9/11 victims' relatives, survivors, rescuers, among other people, are expected to gather at the World Trade Center to remember the horrific day that saw the landmark twin towers collapse, the Pentagon burn and a field in Pennsylvania smolder.

Nineteen Al Qaeda terrorists were said to have hijacked four airplanes for carrying out the suicide attacks in the U.S. 16 years ago. Two of the planes targeted the twin towers of the World Trade Center in New York City, the third plane hit the Pentagon just outside Washington, D.C., and the fourth plane crashed in a field in Pennsylvania.

The American Airlines Boeing 767, which was loaded with 20,000 gallons of jet fuel, crashed into the north tower of the World Trade Center (WTC), burning a hole near the 80th floor of the 110-story skyscraper, instantly killing hundreds and trapping hundreds of others in higher floors.

Just 18 minutes after the first plane crashed into the WTC, a second Boeing 767 — United Airlines Flight 175 — sliced into the south tower near the 60th floor. The impact resulted in a massive explosion that collapsed the twin towers in a massive cloud of dust and smoke. The structural steel of the skyscraper apparently could not withstand the tremendous heat generated by the burning jet fuel.

As millions watched the events unfold in New York, American Airlines Flight 77 crashed into the west side of the Pentagon military headquarters, killing 125 military personnel and civilians, along with all 64 people aboard the airliner.

A fourth California-bound plane — United Flight 93 — was hijacked about 40 minutes after leaving Newark Liberty International Airport in New Jersey. Those on board the jet had learned about the events unfolding in New York as the plane delayed in taking off. A group of passengers and flight attendants planned an insurrection, fighting the four hijackers, who had taken control of the plane and were in the cockpit.

The passengers and flight attendants attacked the cockpit with a fire extinguisher. The plane flipped over and sped toward the ground at upwards of 500 miles per hour, crashing in a rural field near Shanksville in western Pennsylvania.

The plane's target still remains unclear but theories refer to the White House, the U.S. Capitol, and the Camp David presidential retreat in Maryland, or one of several nuclear power plants along the eastern seaboard.

However, many believe it was not possible for just 19 people to carry out such a deadly attack. Conspiracy theorists have claimed over the years that the United States government was involved in the attacks. Here are some of the popular theories that are still believed by skeptics.

Jet Fuel Can’t Melt Steel Beams: Theorists claimed that American Airlines Flight 11 and United Airlines Flight 175 — the planes that struck the North and South towers of the World Trade Center complex in New York City — wouldn’t have been able to produce enough heat to melt the steel beams of the buildings. They claimed that some other weapon, most likely a planned explosion or military grade missile was used, which resulted in the collapse of the towers.

Holes On The Towers Aren’t Right: The American Airlines Flight 77 left behind two 75-foot and 12-foot holes in the Pentagon building but theorists claim that there was no way that a 125-foot jet made such small dents, giving rise to concerns that some debris from the crash site may be missing. This led to speculation of cover-ups.

Puffs Of Dust Show Controlled Detonation: A book by Eric Hufschmid titled, "Painful Questions: An Analysis of the September 11th Attack" claimed the concrete clouds that gushed out of the buildings are not possible from a mere collapse and they rather occurred due to explosions.