The plane, a Vickers Viscount, was on a flight from Cork to London Heathrow when it crashed into the sea near Tuskar Rock without warning. There were no survivors.

St Phelim was an 11-year old Viscount with the Vickers aircraft very popular with Aer Lingus for short and medium haul flights. A total of 20 were in service over almost two decades with the carrier. The passengers and crew were from Switzerland, Britain, the U.S., Sweden, Belgium and Ireland with 36 of the 61 from the Cork area. One of the four crew members, Air Hostess Anne Kelly (19), was from Wexford. Only 14 bodies were ever found.

Mystery still surrounds the accident with various theories over the years ranging from an accident collision with a Royal Navy/Royal Air Force drone through to a catastrophic failure of part of the aircraft fuselage. Ten years ago, a retired Naval engineer claimed he spotted an unusual piece of debris being recovered from the sea near the St Phelim crash site. Moss Egan was on board the L.E. Cliona and spent several weeks at sea, working alongside the British Navy, trying to recover the wreckage of the aircraft in 1968. He said he recalled one discovery in particular, of something which many believe was part of a target drone, a piece of equipment used to test the accuracy of missiles. Mr. Egan said that it was taken away and never seen again.

Although the investigation into the crash lasted two years, a precise cause for the tragedy was never determined. There has long been popular speculation that the plane was shot down by a British experimental missile. A base in west Wales, Aberporth, was the most advanced British missile testing station at the time.

The tragedy has been the subject of books and many column inches over the years and other theories and claims have included that the accident was in fact caused by a mid-air collision between the plane and a French-built military aircraft which was training with the Irish Air Corps.

However, a report in 2002 by French and Australian experts ruled out the possibility that the Viscount was hit by another aircraft or missile. The international study concluded that the cause may have been as a result of structural failure of the aircraft, corrosion, metal fatigue, ‘flutter’ or even a bird strike.