More than a million fake electronic parts from China have been found in US military aircraft, posing a risk to national security, an investigation has revealed.
A report by the US Senate uncovered 1,800 cases of bogus parts - including some in special operations helicopters and the US Air Force's largest cargo plane.
The total number of individual components involved in these cases exceeded one million, the Committee on Armed Services publication said.
"This flood of counterfeit parts, overwhelmingly from China, threatens national security, the safety of our troops and American jobs," committee chairman Senator Carl Levin said.
"It underscores China's failure to police the blatant market in counterfeit parts - a failure China should rectify," he added.
As part of a year-long investigation , the US Government Accountability Office created a fictitious company and purchased electronic parts on the internet.
Of the 16 items bought, all were counterfeit and some had bogus identification numbers.
The components came from suppliers based in China - which Senator Levin described as the "epicentre of electronic part counterfeiting".
The report accused Beijing of openly allowing counterfeiting operations, and said attempts by officials to get visas to travel to China as part of the probe had failed.
US authorities and contract companies contributed to the problem by not detecting the fakes and routinely failing to report them, the report said.
The Defense Department was also criticised for lacking "knowledge of the scope and impact of counterfeit parts on critical defence systems".
Committee member Senator John McCain said the prevalence of bogus parts made the country vulnerable and posed a risk to "our security and the lives of the men and women who protect it".
"The Department of Defense and its contractors must attack this problem more aggressively, particularly since counterfeiters are becoming better at shielding their dangerous fakes from detection," he said.
The fakes included parts in the electromagnetic interference filters used in night missions and in the operation of "hellfire" missiles on SH-60B Navy helicopters.
They were also found in memory chips in the display systems of C-17 Globemaster III and C-130J military cargo planes, and in the Navy P-8A Poseidon aircraft.