The circumstances leading to this serious incident were numerous. The first link in the chain of events was initiated by the Commander of AIH 065 (A330) requesting a westbound clearance for the oceanic entry point SOMAX for a time which was one hour later than actuality, his 1145 hrs request should have been 1045 hrs. This one hour error was not picked up by the Scottish Oceanic Control Area (OCA) based at Prestwick, whose callsign is Shanwick. OCA processed and approved the pilots requested clearance for 1145 hrs at Flight Level (FL) 370 at SOMAX, on North Atlantic Track (NAT) ECHO. AFR 3671 (B747), which was on an eastbound track at FL 370 also, estimated SOMAX at 1109 hrs. Thus, there were two aircraft on reciprocal tracks approaching the same Reporting Point, SOMAX, and at the same Flight Level, 370. AIH 065 entered Shannon Oceanic Transition Area (SOTA) and came under Shannon Radar control on handover from UK ATC (Appendix A). The Sector Controllers in Shannon, in turn, did not pick up on the one hour error and gave Shanwick a revised estimate of 1148 hrs, which was plus three minutes on the original estimate for AIH 065 at SOMAX. Shanwick queried this new estimate and it was only then that the one hour error in the AIH 065 estimate and its significance was fully realised by both the Shannon and Shanwick Controllers respectively. Flight level separation instructions were then initiated by Shanwick.
Contemporaneous to these unfolding events the pilots of AFR 3671 and AIH 065 later reported observing, on their onboard anti-collision device, the Traffic Alert and Collision Avoidance System (TCAS), Traffic Advisories (TAs), as AIH 065 was descended by Shanwick to FL 350. The general area of the incident is West of 15º West, at approximately 50°N 1630° W, and is therefore outside the area of responsibility of Shannon ATC. It is also outside the area of coverage of Shannon Radar. In this non-radar environment over the North Atlantic the surveillance element of ATC relies on pilots "position reporting".