Richard Porter was aboard a Frontier Airlines flight preparing to depart when another passenger became concerned about his statements, DPD said.

DENVER — A man who had boarded a Frontier Airlines flight to depart Denver was arrested at Denver International Airport (DIA) Thursday night after a fellow passenger became concerned about statements he made, according to a probable cause (PC) statement for his arrest from the Denver Police Department (DPD).

Richard Porter was arrested and is being held at the Denver Jail on a charge of endangering public transportation.

Officers with DPD responded to Gate A 46 in Concourse A around 8 p.m. Thursday for a report of a disturbance on Frontier Flight 665 that was preparing to depart, the PC statement says.

An unnamed passenger said she was sitting next to Porter when he began talking to her about things she "found troubling," according to the document. She said Porter was talking about where the safest parts of the plane were in a crash and how to react in an emergency, the PC statement says.

After he made those statements she glanced over at a text message he was sending, according to the PC statement. The text of that message is redacted in the document, but the woman said she took it to mean, "he was threatening people" and that "he intended to do something to cause the plane to crash and kill everyone on board," the PC statement says.

She contacted the flight crew about her concerns and the airline removed Porter from the plane.

Porter was then contacted by an officer with DPD. That officer said Porter immediately identified himself as a "DOD employee" and seemed angry he was being contacted, the PC statement says.

Despite that, Porter was cooperative with the officer and allowed him to look at the messages on his phone.

The officer pointed to the last message Porter had sent and explained that was why he was being contacted. The officer said Porter "seemed to shrug it off," according to the PC statement.

He was taken into custody and booked into Denver Jail.