Eighteen years have passed since the September 11, 2001 terrorist attacks in the United States. 18 years ago, al-Qaeda terrorists carried out the deadliest attack, hijacking four planes to crash into the twin towers of the World Trade Center in New York and hit the Pentagon, according to BGNES.

Flight 93 is the fourth aircraft. It was the passengers of Flight 93 who united against the abductors and prevented them from hitting the US capital again. The plane crashed in a field near a small Pennsylvania town where a monument called the Tower of Voices was build.

With 2,996 people killed and more than 6,000 injured, the attack remains the deadliest in US history. It threw the United States into a chain of wars against Islamic jihadists.

Flight 77 crashed at the Pentagon's military headquarters. All 59 passengers and crew aboard the plane were killed along with another 125 personnel stationed at the Pentagon.

In addition to the 9/11 killings, thousands of rescue volunteers, construction workers and residents have developed illnesses, many of which result from the inhalation of toxic fumes.

Today, the United States will commemorate the anniversary of the attack and pay tribute to the "heroes" in front of the Memorial erected on the site of the World Trade Center in New York. President Donald Trump will also honor the memory of those killed. A ceremony marking the manifestations of heroism in the events of September 11, 2001 will also take place in the Pentagon, Virginia, and in Shanksville, PA.