Anna is a twelve-year-old aspiring journalist and the daughter of a United States senator. As a descendant of Paul Revere, she possesses a natural enthusiasm for civics, history, and current events. She actively seeks the truth and pushes the other children to investigate the missing Star-Spangled Banner while stranded at the airport.

José is a quiet, observant twelve-year-old who prefers the company of books to the chaos of the airport. He is the descendant of Mexican artist Frida Kahlo and the grandson of migrant workers. He approaches problems practically and often relies on quotes from historical figures and literature to make sense of stressful situations.

Henry is a twelve-year-old boy who uses video games to distance himself from the people around him. Dealing with the grief of his mother's death and his father's remarriage, he remains detached from the history his Aunt Lucinda loves. However, his gamer instincts give him an unexpected understanding of strategy and courage when the children face actual danger.

Robert Snickerbottom is a United States senator currently running for president. Recognizing the political opportunity in the stolen flag, he assigns his campaign staff to investigate the crime at the airport. He projects a folksy, larger-than-life persona complete with a cowboy hat, though he shows little patience for the children.

Sinan is an eight-year-old boy whose parents are members of an international orchestra called Sounds for a Small Planet. Because English is not his first language, he keeps a notebook where he draws literal interpretations of American idioms. He looks up to the older children while moving through the stressful environment of the snowed-in airport.

Hammurabi is an oversized, energetic gray poodle belonging to Sinan. Named after an ancient king, he is far more interested in stealing food and chewing on his squeaky toy than acting regal. His unpredictable behavior occasionally causes trouble for the stranded passengers.

Claude is a man waiting out the snowstorm at the airport who draws the children's suspicion. He works as a baggage handler and has a prominent tattoo of a curled-up snake on his arm. His hurried movements around the terminals make him the primary target of Anna's amateur investigation.

Molly is Anna's mother and an accomplished journalist. She is a member of the Silver Jaguar Society, a secret group dedicated to protecting historical artifacts. Her professional success serves as the primary inspiration for Anna's own ambitions.

Senator Hobbes is Anna's father and a supportive colleague of Senator Snickerbottom. He strongly favors immigration reform, which influences his political alliances. He spends much of the snowstorm on his phone coordinating with other politicians.

Maria is José's mother and a highly skilled historical textiles expert. She works closely with the Smithsonian to restore the original Star-Spangled Banner. Her intense dedication to the flag often keeps her away from her family for weeks at a time.

Mr. McGilligan is José's father and a television meteorologist. He is initially thrilled by the massive snowstorm grounding the flights, but his excitement turns to panic when his wife becomes a suspect in the flag theft.

Aunt Lucinda is Henry's relative who temporarily watches him while his father is on a honeymoon. She is deeply passionate about American history and wears a large silver charm bracelet. Her enthusiasm for museums largely annoys her nephew.

Earl is Senator Snickerbottom's shorter, scrawnier brother who works on his campaign team. He suffers from severe allergies that cause him to sneeze loudly and frequently. He handles many of the practical tasks for the senator's investigation at the airport.

Vincent Goosen is the notorious leader of an international art theft ring called the Serpentine Princes. Though he does not directly interact with the children, his reputation and distinctive snake tattoo make him a looming threat in their investigation.

Betty Frumble is the governor of Vermont who is running for president against Senator Snickerbottom. Anna secretly admires her intelligence, eloquence, and unique approach to connecting with voters through baked goods.

Erma Emma Jones is the director of the Smithsonian Museum of American History. She is responsible for the overall security and display of the nation's most precious artifacts, including the Star-Spangled Banner.

Jeff Brodie is a curator at the Smithsonian Museum of American History. He manages the direct access to the Star-Spangled Banner and attempts to follow strict security protocols before being called away on an emergency.

George is an airport baggage handler who works among the massive conveyor belts. He is easily distracted by children asking about his job and enjoys telling stories about his experiences working with luggage.