The flight NW-2 was in a holding near Chiba (40nm south of Narita) about 30 minutes before landing with seatbelt signs turned on, when the airplane encountered severe turbulence and suddenly departed its assigned altitude of 15000 feet. A number of passengers, who had not fastened their seatbelts, were thrown out of their seats and hit the ceiling. The crew reported about 2-3 injuries via radio, but did not declare emergency. The landing, 30 minutes later, was safe. A total of 43 passengers were injured in the upset and were brought to hospitals. Initially reported two serious injuries turned out less severe. However, Japanese officials reported later, that one passenger received a serious injury (neck fracture). Northwest Airlines said, no crew got injured in the accident.