On September 11, 2001, United Flight 23 was grounded when the World Trade Center was hit, but it might have been another plane hijackers planned to weaponize in the terrorist attack — and, our documentary covering it all is now available on YouTube.

“TMZ Investigates 9/11: The Fifth Plane” — the result of a 6-month investigation — takes viewers through the litany of suspicious activities that prompted the FBI to look into whether the plane was also part of the horrific plot that fateful day.

We interviewed 3 flight attendants, the pilot, the United dispatcher, and a member of the 9/11 Commission … who reveal a story about suspicious passengers who were a bit too eager to get into the air, and uniformed individuals running through the cabin after the plane was evacuated.