The south tower of the World Trade Center twin towers begins to collapse after hijacked planes crashed into the towers on September 11, 2001 in New York City.(AP Photo/Richard Drew)

This week, Monday, September 11, marks the 16th anniversary of the 2001 terrorist attacks, where 19 militants associated with the Islamic extremist group al-Qaeda, hijacked four domestic airplanes and carried out suicide attacks targeting the U.S. As a result, two planes were flown into the twin towers of the World Trade Center, located in New York City. The third plane hit the Pentagon outside of Washington D.C., and the last plane crashed in a field in Pennsylvania.

At the World Trade Center, 2,763 people died after the two planes crashed into the twin tower. The death toll also includes, 343 firefighters and paramedics, 23 New York City police officers and 37 Port Authority police officers.

At the Pentagon, 189 people were killed, including 64 on the American Airlines Flight 77. On Flight 93, where the plane crashed in Pennsylvania, 44 people died.

Firefighters make their way through the rubble after two airliners crashed into the World Trade Center in New York bringing down the landmark buildings Tuesday, Sept. 11, 2001. (AP Photo/Shawn Baldwin)

Since the attack, the U.S. put into place several initiatives to combat terrorism.

In the 1970’s, TSA used metal detectors. Today, living in a post 9/11 era, airlines are equipped with body scans and complete enhanced pat-downs. Some pilots are armed and air marshals have been put in place to thwart potential threats. As the years went by, TSA banned water bottles, asked flyers to remove their shoes, belts, hats, etc., along with other approved security procedures. TSA no longer discriminates; everyone from infants to the elderly are thoroughly searched to ensure security and the safety of travelers and employees.

Aside from the invasive pat-down given by TSA, some citizens have become fearful of flying and fearful of foreigners.

A shell of what was once part of the facade of one of the twin towers of New York’s World Trade Center rises above the rubble that remains after both towers were destroyed in a terrorist attack Tuesday, Sept. 11, 2001. The 110-story towers collapsed after two hijacked airliners carrying scores of passengers slammed into the sides of the twin symbols of American capitalism. (AP Photo/Shawn Baldwin)

On January 27, President Donald Trump signed an executive order temporary barring people from seven Muslim-majority countries, as part of his promise to “make America great again.” One week later, a federal judge in Seattle suspended the ban nationwide, allowing visitors to once again freely travel in and out of the U.S.

According to Trump the refugee program was needed in order to give government agencies time to develop a “stricter” vetting system and ensure individuals who pose a national security threat were not issued visas.

“This is not about religion – this is about terror and keeping our country safe,” said Trump. “There are over 40 different countries worldwide that are majority Muslim, that are not affected by this order.”

On the morning of the 16th anniversary, President Trump arrived at the Pentagon, the site where one of the four planes crashed into, to mourn the lives of those who were killed and to ensure the safety of others.

“The terrorists who attacked us thought they could incite fear and weaken our spirit,” said Trump.  “But America cannot be intimidated, and those who try, will soon join the list of vanquished enemies who dared to test our mettle. We are making plain to these savage killers that there is no dark corner beyond our reach. When America is united, no force on earth can break us apart.”

Every year, family members, survivors, rescuers, and others, gather in unison across the nation, at events and memorials created  to honor the victims and heroes of the 9/11 tragedies.