A Tokyo-bound flight carrying the model Chrissy Teigen and her musician husband John Legend turned back to LA after someone reportedly boarded in error.
According to Ms Teigen, the passenger boarded at LAX airport with a ticket for a different airline, although this was not confirmed by authorities.
The plane turned back four hours into the flight, over the Pacific Ocean.
The airline, All Nippon Airways (ANA), said only that there had been a problem with a customer's "flight arrangement".
Adonis Cutchlow, of the LAX Police, told the LA Times there had been no criminal or illegal activity on board the plane, and it was not clear why it had turned back.