The US Navy was investigating Thursday how several chunks of one of its aircraft -- including one around 2.2 metres (seven feet) by one metre -- fell off as it flew back to its base in Japan.
Six pieces from an EA-6B Prowler, including a part of the engine cover, plunged to earth as the plane flew over Yamato, near Tokyo, causing "minor damage to a privately-owned vehicle", the US Navy said.
The aircraft, from the US Navy's Yokosuka base in Kanagawa prefecture, "was returning from a routine training flight when the parts... fell off and the plane landed safely."
An official from Yamato city said aircraft regularly dropped debris, adding that a house was damaged in 2010 by a piece of falling metal.
The US has around 50,000 troops stationed in Japan at bases all over the country and tensions with host communities are not uncommon.
"The Navy deeply regrets any inconvenience this event may have caused its neighbours," said a statement from the US forces.