A United Airlines flight crew is coming forward with what they say could've been a close call on 9/11.

Members of the flight's crew said their Boeing 767 aircraft could've been the target of an attempted, fifth hijacking attempt.

Flight 23, slated to fly from John F. Kennedy Airport in New York to Los Angeles International Airport, averted takeoff when an air traffic controller learned of the attack on the World Trade Center.

Members of the flight's crew recounted bizarre interactions with passengers on board the ultimately grounded flight before takeoff, speaking in a new TMZ documentary "TMZ Investigates: 9/11: The Fifth Plane." The full documentary will be released on Monday.

TMZ said it investigated the “suspicious" activities that took place before the flight's takeoff for six months.

The flight crew recounted passengers behaving bizarrely in the first class segment of the plane before takeoff -- including one person wearing an Islamic hijab, whom crew members believed was impersonating a woman, according to the New York Post.

The suspicious passengers urged crew to take off, instigating an argument with their impatience.

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The crew members said another passenger in business class was sweating profusely, according to the Post.

In a disturbing twist, box cutters were later found stowed inside the first class area of the plane parked next to Flight 23.

The plane had one tail serial number that differed from Flight 23, and flight Captain Tom Mannello believes an airport insider placed the impromptu weapons on board for use as weapons.

The captain later witnessed two uniformed individuals rummaging through Flight 23 after passengers were disembarked -- and believes they could've been looking for the stowed box cutters in question.

Hijackers used the tools to overpower flight crews on the other planes hijacked during 9/11 -- using three passenger jets as weapons against the World Trade Center and the Pentagon.

Passengers succeeded in overwhelming hijackers aboard a fourth flight, forcing them to crash the plane in a field in Somerset County, Pennsylvania.

"There is a good chance that somebody was plotting to try to use our airplane as a weapon of mass destruction," Mannello said of the cancelled flight.

Flight attendant Sandy Thorngren also believes the aircraft was a target of the terrorists.

“I definitely think that Flight 23 from JFK to LAX was the fifth plane," she said.

“And that’s what scares, haunts me to this day.”

The 9/11 attacks -- orchestrated by the Islamic terrorist group al-Qaeda -- represent the most devastating single attack on the American homeland in the nation's history.

No arrests have ever been made in connection to Flight 23.

The federal 9/11 Commission investigated the terrorist attacks extensively. Flight 23 isn't mentioned in the commission's nearly 600-page final report.

This article appeared originally on The Western Journal.