Brace yourselves, this will be an uncomfortable IMO...
Charlotte never left on a jet plane. She didn't even arrive at the airport. Charlotte did stay with her sister, Carole Fryday, and her husband, Tom, at their home in Eatontown, New Jersey where he was stationed at the military base. However, Charlotte wrote to her parents saying that she wanted to come home to Detroit, Michigan. So they arranged a direct flight from Newark to Detroit.
Charlotte's luggage did arrive at Detroit and her parents were there to pick her up, but she didn't show. Her brother Ed said they panicked and soon, security guards, airport police, and the Detroit PD were at the scene. Carole was questioned and she said she put Charlotte on the plane. Her husband Tom was never questioned. In 2000, at Charlotte's stepfather's deathbed, Carole said Charlotte was misbehaving and had even gotten pregnant which resulted in an abortion at the Eatontown military base. Their younger sister, Laurie, doesn't believe this narrative.
And now for the disturbing part. After Charlotte's stepfather died, her brother, Dewaine, said that when Charlotte wrote to their parents, she also wrote to him begging him to pick her up because Carole and Tom were mistreating her. Dewaine couldn't do that because he was in the Army, but he did go AWOL looking for Charlotte when she vanished. Laurie has revealed that both Carole and Tom were involved in many illegal activities while he was stationed at the base including dealing with drugs.
So here's what I think...
Charlotte died at the hands of her sister and her husband. I think the reason why was that she was going to tell her parents about their illegal activities. And you know, I wouldn't be surprised if she said Tom Fryday was molesting her too. I think she was killed shortly before the flight was to take place. Carole and Tom simply took her luggage to the airport and dropped it off. As for her body, I think it's still buried in Eatontown.