Two brothers who boarded a Tokyo-bound plane that turned around four hours into the flight could be facing charges from the FBI.

The men, who have nearly identical names, allegedly boarded the All Nippon Airways flight at Los Angeles International Airport using a single boarding pass, sources told ABC News. One of the brothers had a flight booked on the ANA flight, the other on a United Airlines flight also bound for Tokyo.

The brothers are said to have duplicated a boarding pass and it's unclear how the brother with the United ticket found a seat on the plane. Besides being male American citizens, their identities have not been revealed.

The airline made the decision to turn around, according to the report, and the brothers were interviewed by authorities when the flight landed in Los Angeles.

"During the flight, the cabin crew became aware that one of the passengers boarded the incorrect flight and notified the pilot," ANA said in a statement to ABC. "As part of the airline’s security procedure, the pilot in command decided to return to the originating airport, where the passenger was disembarked."

FBI investigators told ABC they are not ready to make any arrests, but if they determine there was intent to board the incorrect flight, one of the brothers could be accused of being a stowaway, a federal crime punishable by up to five years in prison. ANA could also be fined by U.S. Customs and Border Protection for failing to make an accurate headcount and allowing the passenger on board in the first place.

Model Chrissy Teigen, who was on board the flight with her husband, singer John Legend, live-tweeted the chaos of turning the aircraft around after four hours.

At one point, she complained of being "on a flight to nowhere."

Passengers reported being compensated 30,000 yen, or about $265.