Originally Posted by Qwkynuf

What the others mean by "preclearance" in this case, is not things like TSA PreCheck or Global Entry. What they are referring to is that some international airports - most of the major Canada ones, Dublin and Shannon in Ireland, a few Caribbean islands, and Abu Dhabi have US Customs on site, so you clear US Customs before departure, and then when you arrive at your US destination you are treated like a domestic passenger and just dumped into the airside concourses. It *can* be an overall better experience, but it can also just move the annoyance to a different location.