A new report from TMZ on Saturday claims the 9/11 attacks may have included a fifth plane but it was denied takeoff at the last second. Flight attendants and a pilot for United Flight 23, which was scheduled to leave New York’s JFK airport for Los Angeles that morning, reportedly noticed “a series of suspicious activities” onboard—like first-class passengers who rushed flight attendants to take off, and a man disguised as a woman. The flight was ultimately called off as it taxied because the first hijacked plane had just crashed into the North Tower of the World Trade Center. Once back at the gate, those interviewed by TMZ said they saw men running toward their plane, and that box cutters were found in the seat-back pockets on the plane next door—items they feared were actually meant to be on their flight. TMZ reported that the FBI investigated, but the incident wasn't mentioned in the official 9/11 Commission report. TMZ’s full findings, supposedly the result of a six-month investigation, will air on Fox on Monday evening as part of a special episode.