The author of “Secret on the Tarmac” revealed new details Monday about the secretly held 2016 meeting between former President Bill Clinton and Attorney General Loretta Lynch.

“We knew something had occurred that was a bit unusual. It was a planned meeting. It was not a coincidence,” journalist Christopher Sign told “Fox & Friends" about the explosive meeting that cast a negative light over the FBI's investigation into Hillary Clinton's use of a private email server while she was secretary of state.

At the time, then-candidate Donald Trump criticized Bill Clinton via Twitter for potentially trying to interfere with the investigation.

Trump had publicly questioned the meeting at Phoenix's Sky Harbor Airport, after which Clinton and Lynch claimed the conversation centered around their grandchildren. The meeting occurred just days before the FBI decided it would not recommend criminal charges against Hillary Clinton.

"Does anybody really believe that Bill Clinton and the U.S.A.G. talked only about 'grandkids' and golf for 37 minutes in plane on tarmac?" Trump asked via Twitter at the time.

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Sign said: “[Secret on the Tarmac] details everything that they don’t want you to know and everything they think you forgot, but Bill Clinton was on that plane for 20 minutes and it wasn’t just about golf, grandkids, and Brexit. There's so much that doesn’t add up."

He said that his source who was there outlined that when Clinton arrived at the airport, he was waiting for Lynch.

“He then sat and waited in his car with the motorcade, her airstairs come down, most of her staff gets off, he then gets on as the Secret Service and FBI are figuring out ‘How in the world are we supposed to handle this? What are we supposed to do?’” Sign said.

“As journalists, you have to ask yourself, why are people not delving into this? Why are we not looking into what exactly happened?

Sign said that Lynch in December of 2018 testified before the House Oversight Committee.

“She mentioned that Bill Clinton flattered her, talked about Eric Holder, talked about how things were going at Justice, talked about her job performance, not this golf-grandkids, Brexit.”

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Sign said that his family has received death threats for telling the story.

“This story isn’t about right or left, Republican or Democrat, it’s about right and wrong and journalism."

In response, Bill Clinton said he was "offended" over the allegations of misconduct regarding the tarmac meeting.

“I thought, you know, I don’t know whether I’m more offended that they think I’m crooked or that they think I’m stupid,” Clinton told investigators, according to a 2018 report released by Justice Department Inspector General Michael Horowitz.