This reminds me, Shannon airport were making a big thing about US pre-clearance to dramatically speed up times taking to get into your fine land. It was an idea for us when they had regular flights from Bristol to Shannon, and plenty of deals to the US but sadly for me they have cut those flights to Shannon from here.
http://www.shannonairport.ie/gns/passengers/prepare/us-preclearance.aspx
http://www.shannonairport.ie/gns/passengers/prepare/us-preclearance.aspx