Bolivia, Burma, Australia, Turkey and the US were just some of the countries listed on the website of Smyth Aerospace Manufacturing Ltd, which offered "worldwide sales and engineering".
"Organisations like this can locate anywhere," explained Mr David Learmount, operations and safety editor of Flight International magazine. "Shannon is known for its good links to America. Most counterfeit parts come from or go to the US where this is big business."
Some of the 10 people "helping gardai with their inquiries" this week were US nationals, who set up business in the Shannon industrial estate four years ago.
The Irish Aviation Authority (IAA) moved quickly to dispel public fears about safety, and a spokeswoman said there was no evidence of any risk to Irish airlines. According to a source in non-commercial aviation, the company did not have a good reputation in the Irish industry and was not IAA-approved.
Mr Declan Conroy, a spokesman for Aer Lingus, said Ireland had rigorous controls to ensure aircraft maintenance companies dealt only with reputable suppliers of engine parts. "Something like this would never be covered up because issues of safety are our lifeblood," he said.
Suspicions about the Shannon-based company first surfaced in the US when second-rate aviation parts were shipped to the military, and it now appears the Irish military has also been duped.
The Air Corps said that despite turning down a business advance from the company they could trace deliveries from Smyth Aerospace to their suppliers. Yesterday they grounded seven Cessna and seven Marchetti fixed-wing aircrafts as investigations continued.
A spokesman for the Defence Forces said the parts concerned were "very minor", such as bolts and washers, but checks were nevertheless being made.
The fears are well grounded. Faults in minor parts are now believed to have caused a Danish airliner to crash after take-off from Oslo in 1989, killing all 55 people on board. Air accident investigators found the aircraft had broken up in the air.
The tail fin was found some distance from the rest of the wreckage, and the nuts and bolts that had secured it to the fuselage were made from ordinary steel rather than specially hardened and heat-treated steel. The same year a DC-10 crashed in Chicago when bolts securing the engine to the wing became loose and fell off.
Mr Learmount says the accident in the North Sea is the only one to date linking commercial airlines to counterfeit parts. "Small aircraft and helicopters are the ones really at risk. It is a very serious issue for the industry, but passengers have no need to panic.
"It's not that they will never fly on a plane that doesn't have a counterfeit part. They probably will, but aircraft have so many backup systems that it's not a question of a plane tumbling out of the sky if a part fails," he says. But industry experts disagree on the level of danger, and Philip Butterworth-Hayes, editor of the Jane's Aircraft Component Manufacture, stresses the airlines cannot be complacent. "If you consider there are a million parts in a 747 the difficulty in keeping track of them and the huge number of things that can go wrong is clear," he said.
Smyth Aerospace offered parts for the well-known passenger aircraft, the Boeing 747 and 737, on its Internet site alongside the McDonnell DC-10, F-4 and Cessna A-37.
Mr Butterworth-Hayes said the aviation industry faced two main problems. "The first is criminals who become involved in bogus spare parts because the mark-up price on an aircraft part can be higher than crack cocaine. It can cost them £1 to manufacture it and then they can sell it on for £100."
The second problem is the billions of pounds worth of genuine aircraft parts in storage that are not accompanied by documentation. However, he said the situation had improved in recent years with the increased use of electronic and barcode tagging.
The issue becomes prominent at regular intervals in the US. The US National Transportation Safety Board has found unapproved parts were "causal factors" in numerous accidents and emergency landings with airlines, small private planes, cargo carriers, crop-dusters and helicopters.
The Federal Aviation Administration (FAA) estimates that 166 accidents or serious mishaps between May 1973 and April 1993 were due to bogus parts. Its guidelines acknowledge that unapproved parts are not easy to detect but warn that doctored parts, illegally modified parts, old parts sold with falsified records and overproduced parts sold cheaply bypassing quality control are all unacceptable.
Between 1992 and 1999 more than 350 cases involving unauthorised parts were prosecuted in the US. Earlier this year a counterfeit parts operation was broken in Florida. The man who sold unapproved parts to federal agents operating an undercover parts business faces a maximum penalty of five years' imprisonment and a $250,000 fine if convicted.
The Air Transportation Improvement Act, being debated on the floor of the US Senate, includes a provision aimed at combating the trade. If passed, the act will prohibit anyone convicted of an offence involving counterfeit aviation parts from obtaining an FAA certificate or future employment in the industry.
According to Republican Senator Orrin Hatch, federal investigators have discovered that more than 600 helicopters sold to US civilians and NATO had counterfeit parts.
In Britain in 1991, after a two-year investigation, seven men were sentenced for their role in a racket that involved old parts stolen from warehouses belonging to British Airways and sold on. That year the Civil Aviation Authority in Britain said it was aware of seven private aircraft accidents where illegal parts were suspected.
In a morbid twist, parts are often stolen from crash sites before entering the second-hand market. In 1995 an American Airlines aircraft crashed into a Colombian mountainside, killing 164 passengers and crew. Before air accident investigators could examine the wreckage it was found that more than 500 parts from the aircraft were missing.
In August Irish air accident experts had a similar experience while investigating a helicopter crash in Co Longford, which killed two people. The Inspector of Accidents at the Department of Enterprise, Mr Frank Russell, described the theft of the parts as "outrageous" although gardai said they believed people had only taken "souvenirs".
