Man who checked hijackers onto Flight 77 on 9/11 says it's haunted him ever since

One of the American Airlines employees who was working on 9/11 has spoken out about unknowingly checking in the men responsible for the attacks.

Most Americans who were alive on 11 September, 2001 will be able to tell you what they were doing on that day.

People remember watching the events on the news, seeing smoke billowing from the Twin Towers, attempting to get in touch with loved ones or even being forced to flee the area themselves.

Vaughn Allex was at work at the American Airlines ticket counter at Dulles International Airport outside of Washington, DC.

It started off as just another day as he checked in passengers for Flight 77, but Allex had no idea the flight would later be hijacked and crashed into the Pentagon, the home of the US Department of Defense, killing 189 people.

In an interview with Story Corps 15 years after 9/11, Allex spoke how the realization that he'd checked in the hijackers responsible for the attacks affected him later in life.

Story Corps

He recalled how two men were running late to board their flight and came rushing up to his check-in desk.

Those two men were Salem and Nawaf Al-Hazmi, brothers who would later be identified as part of the five-man team that hijacked the American Airlines flight and crashed it into the Pentagon.

Allex didn't fully realize what small part he had unknowingly played until the next day, when he went into work and 'people wouldn't look at [him] in the eye'.

He still remembers many of the other people he checked onto Flight 77 that day, and spoke about how difficult it was to come to terms with 9/11.

"I checked in a family that was a retiree and his wife, I had time to talk to them," he recalled.

The plane crashed into the Pentagon. (Federal Bureau of Investigation via Getty Images)

"There was a student group and I checked in a lot of those kids, and the parents, teachers. They were gone, they were just all gone. Once it became known people didn't talk to me."

"I felt that there was no place for me in the world, there were all these support groups and I didn't belong there because how do I sit in a room with people that are mourning and crying and they're like 'what's your role in this whole thing' well I checked in a couple of the hijackers and made sure they got on the flight."

Allex added that while the incident is something that has haunted him ever since and he won't ever forget, he has in recent years been more able to talk about it.

Of course, there was no way Allex could have known what was about to happen after he checked in the two late passengers.