The editorial in The Irish Times of Monday, March 25th, 1968, was headed "Catastrophe". The cause of the previous morning's crash of an Aer Lingus Viscount aircraft, the St Phelim, into the Irish Sea near Tuskar Rock, killing all 61 on board "is not and may never be known", said its writer.

"Sympathy with the victims and their relatives puts all other considerations at a discount at this stage. To everyone in Ireland it will have the poignancy of a family tragedy." The editorial continued: "Aer Lingus has a wonderful record . . . There will be no loss of confidence in the company." Had he read Tuesday's report - A Review of the Irish and UK Files on the Loss of the Aer Lingus Viscount, the writer might have held judgment. He might also have had something to say about the assiduousness of the then Department of Transport and Power.

Published by the Department of Public Enterprise, its authors, Kevin Humphries and Graham Liddy of the Department's Air Accident Investigation Unit, reach 41 conclusions. Among them are that there were "serious errors in the Maintenance Operating Plan of EI-AOM [the St Phelim] at the time of the accident. These errors originated within Aer Lingus".

The company also mislaid critical paperwork from routine maintenance checks. Despite this, the Department of Transport and Power issued a Certificate of Airworthiness to the ill-fated St Phelim seven weeks before it plunged 17,000 feet into 39 fathoms of seawater.

What remains true is that the cause of the tragedy "is not and may never be known". However, Tuesday's review adds solid information to 30 years of speculation, dramatically altering that speculation's focus. The last words heard from the plane's Capt Barney O'Beirne, recorded by London air-traffic control were at 10.58 a.m. on that sunny, early spring Sunday morning.

"Twelve thousand feet spinning rapidly," said Capt O'Beirne.

The Irish Times of the following morning reported sources suggesting "the Viscount could have spun after a jamming of the control flaps on either of the plane's wings".

"Another possible cause of the crash could have been a fault in the tailplanes."

It was not until Richard O'Sullivan, aeronautical officer at the Department, published his investigation into the crash in 1970, that the possibility of the plane being hit by another airborne device, such as a missile or unmanned aircraft, gained currency.

Although he found no evidence of another aircraft in the area, Mr O'Sullivan wrote: ". . . the conclusion that there was such another aircraft in the vicinity is inescapable". The implication for many was of a British military involvement in the disaster.

Problems with the search and salvage operation - which involved delays and mistakes by the British - compounded this suspicion. As Tuesday's review puts it, the suspicion was strengthened because "when the investigator published his report it focused . . . almost exclusively on the possible presence of another aircraft".

It was perhaps an irresistible suspicion that gave rise to hundreds of newspaper and magazine articles, to a 1982 book Tragedy At Tuskar Rock by Dermot Walsh, to several television documentaries - notably a Prime Time report in 1998 - and to numerous parliamentary questions.

Crucially, little was asked, until Tuesday, about the aircraft's maintenance record. Crucially, key information about it was omitted from Mr O'Sullivan's report. Perhaps most crucial of all, the Richard O'Sullivan who conducted the investigation into the loss of flight EI 172 at 12.15 p.m. on Sunday March 24th 1968, was the same Richard O'Sullivan who initialled a Certificate of Airworthiness for the plane on February 6th, 1968.

Among the evidence Humphries and Liddy have viewed is a file, "EI-AOM", newly uncovered by the Irish Aviation Authority. "Two items of concern were found in this file," they write. These were records of the plane's maintenance checks together with research into the plane's maintenance plan carried out after the accident.

This file notes that the "Inspection Operating Plan was changed from Issue 1 to Issue 2 around March 1967", say Humphries and Liddy. "The analysis notes that many errors were made in converting to the second issue of the operating plan, particularly with regard to inspection items being called due at an incorrect time."

These errors should have been picked up, and acted upon, by the Department.

On December 18th, 1967, EIAOM had a routine maintenance check, number 2.04. An internal Aer Lingus memo dated January 3rd, 1968, noted that work-cards from check 2.04 were missing. It also noted "a similar occurrence involved in a recent accident, which was the subject of an investigation".

DESPITE this missing paperwork, a certificate of airworthiness was initialled by Mr O'Sullivan at the Department on February 6th, 1968.

While Tuesday's report stresses there is no evidence linking the plane's maintenance history with the accident, it calls "unsatisfactory" that the same Department staff member certified the plane as airworthy as was responsible for the investigation. It also describes as "incomprehensible" the fact that the maintenance history was omitted from his report.

Many of the key players have died, including Mr O'Sullivan who passed away last month, aged 95. Interviewed by the review in February, he was described as having been "very frail" and who, when asked about missing documents, "could not recall anything".

Few of the Aer Lingus personnel at the time would comment on Tuesday's findings.

Mr Michael Dargan, general manager from April 1967 until March 1974, said that while he "certainly remember the shock of hearing the news, especially as our safety record was so good", the first he heard of the missing maintenance cards was when he read Wednesday morning's papers.

Mr Bart Cronin, then assistant publicity officer heard news of the crash while on a train from Kerry to Dublin. He got off the train at Mallow and went straight to Rosslare, where journalists and relatives were waiting to receive the dead.

He pointed out that everything was then recorded on paper, that there was "a lot of building going on at Dublin Airport" and that files were being "moved about all the time".

This week's review says while "the loss of records and the errors in the Maintenance Operating Plan of EI-AOM must be a matter of concern, the available evidence is that these errors were by no means unique to EI-AOM. There is evidence that there were significant failures in these areas within Aer Lingus . . . and that these were not being detected by the Department".

The Minister has invited two international air accident investigators to cast a fresh set of eyes over the evidence, one of whom, Australian Colin Torkington, is an expert in Vickers Viscount aircraft.

David O'Beirne, who was one year and 10 months old when his father, Barney piloted EI-AOM on its final journey, has one key question for them. "How," he asks, "could they have let a plane take off carrying 61 people, that very possibly was not air worthy?"