Hugo is an eleven-year-old boy traveling from Kenya to New York with his family to seek medical treatment for his younger sister. Burdened by anxiety and a deep sense of responsibility, he is fiercely protective of his sibling. His journey aboard the famous zeppelin forces him to confront his fears, handle intimidating authority figures, and make brave choices to protect others.

Gertie is Hugo's four-year-old sister who is suffering from a life-threatening case of malaria contracted in Kenya. Her illness is the primary reason for her family's urgent trans-Atlantic flight on the Hindenburg. Despite her fragile physical state, she possesses a sharp, unfiltered intuition about the people around her.

Peter Singer is an employee of the Zeppelin Company and a caring single father to his daughter, Marty. He serves as a warm, knowledgeable presence aboard the ship, offering tours and explaining the airship's mechanics. His calm demeanor and fluency in German allow him to handle the high-stress environment of the Hindenburg with quiet confidence.

Colonel Joseph Kohl is a menacing, uniformed Nazi officer aboard the civilian flight of the Hindenburg. Tasked with hunting down an elusive passenger, he represents the encroaching political threat of the Nazi regime. He uses predatory intimidation and psychological tactics to interrogate passengers and maintain tight control over the ship.

Marty is an outgoing, confident girl who is traveling with her father on the Hindenburg. As an experienced zeppelin traveler, she serves as a calming foil to Hugo's anxieties. Her mother passed away four years earlier, making her incredibly close to her father and eager to make friends on the journey.

Hugo and Gertie's mother and father are science professors who recently concluded a research trip in Kenya. They are entirely focused on securing life-saving medical treatment for Gertie in New York. While Mom openly expresses her nervousness about flying, Dad attempts to provide a reassuring presence using facts and logic about the zeppelin's safety record.

Mr. Merrick is a British passenger traveling aboard the airship. He is well-connected and eager to share gossip, contributing to the tense atmosphere by spreading rumors about the real reason Nazi officers are on the civilian flight.

Miss Crowther is an older American woman experiencing the luxury of the Hindenburg crossing. She participates in the dining room conversations and reacts to the escalating political anxieties spreading among the passengers.

Mr. Lenz is a cheerful German passenger who enjoys the smooth, quiet ride of the airship. He provides a brief sense of joviality and local perspective before the atmosphere is soured by the arrival of the military officers.

Panya is a ragged mutt the Ballard family rescued as a stray in Kenya. His name means mouse, and he serves as a vital source of comfort for the ailing Gertie. Relegated to the dark, restricted cargo hold during the flight, his isolation adds to the children's distress.