There are more than 2 USA bound flights from SNN that use the preclearance there. Both Delta and Continental have flights to JFK and EWR respectively, and AA currently have a flight to ORD. The opening hours of the facilities in DUB and SNN are not within Aer Lingus' control, it is provided as a service by the US.
Some airlines opt not to use it as it regularly delays flights. Maybe on the day in question a decision was made to clear the EI-123 on arrival in ORD to keep it running to schedule and to allow the 145 to LAX do the same as a result of less people to process through the facility in DUB.
The best people to have asked were the staff employed to check documentation at the entrance to the preclearance area.
Last edited by CallBell; 18th Sep 2007 at 13:54.
Reason: add last paragraph