A Japan-bound Vietnam Airlines plane was forced to remain grounded for nearly four hours after a passenger spotted a white mouse on the plane. The aviation authorities suspect the mouse might have hitched a ride aboard the plane in the hand luggage or pocket of one of the passengers and eventually escaped. The Boeing 777 from the central city of Da Nang landed at the Hanoi-based Noi Bai International Airport late Saturday and was scheduled to fly to Japan but the flight was delayed after a passenger aboard the plane reported the airplane crew of the mouse.