How does US preclearance work in Dublin?

Question

I am traveling to LAX, and I thought about flying from Dublin, because it has a preclearance station. This station will give me an immigration and customs clearance, so when I arrive at LAX, I will just exit the plane like I was a citizen (don't have to go through CBP check anymore). To go to preclearance, I have to have an already purchased ticket to LAX from Dublin. Now I have purchased a ticket that flies from Dublin through Amsterdam (Netherlands) to LAX.

Question:

1. If I am precleared to enter the US (without an immigration check at LAX upon arrival), how will they know that I have been precleared, and they have to treat me differently from other passengers who are not precleared?

2. Upon arrival at LAX, there are two kinds of lanes, one for US citizens (and permanent residents), and another lane for non-permanent residents. Now normally I would go to the non-permanent resident lane and would have to go through CBP check. But in this case being precleared, will i be able to enter the citizen lane?

Answer 1

Airplanes are pre-cleared, not humans

What happens with pre-clearance is the airplane docks in an area that is under control of US CBP or trusted partners. The airplane is inspected (cleared), then each passenger and their possessions enters this area and effectively is landed in the USA, with immigration done on them, and customs done on their stuff. All is loaded on the airplane, doors shut, US Customs seals slapped on all the doors (not really), and the plane is watched to make sure it doesn't stop in a ramp area to have any cargo or passengers added.

As long as it flies uneventfully to the US, CBP doesn't care where it unloads, and you will not be talking to CBP again (or, anyone). Forget citizen gates, there won't be any gates at all. It may dock at a domestic gate so onward pax don't have to re-clear security. In an emergency it could also divert to a domestic municipal airport like SHD that has no CBP presence, and that's not going to create a serious customs/immigration problem. Imagine you legally entered the US when you set foot on that plane.

This only works if you board a plane that is pre-cleared.

So you see where your plan falls apart. US CBP in Ireland isn't in the business of pre-clearing flights to Amsterdam.

Redesign your journey so your leg which first lands in the US starts in a pre-clearance airport.

By the way, the Irish have a delightful video about it. They seem to be really proud to have a US CBP presence, and they slap an American flag on one of their terminals, almost as if it's US territory! At a certain point, your flight is called for prescreening and you are directed to the TSA area. You scan your documents at a kiosk, then bring your papers to a CBP officer who checks your papers and asks any questions.

Answer 2

"like a citizen" should read "as if I were arriving from another US airport" because citizenship has nothing to do with whether a passenger must clear immigration and customs. Only the point of origin is relevant.

You cannot use preclearance if you're flying through Amsterdam because this statement is incomplete:

To go to preclearance, I have to have an already purchased ticket to LAX from Dublin.

It should actually say

To go to preclearance, I have to have an already purchased direct ticket to the United States from Dublin.

The problems you're asking about do not exist because preclearance applies only to direct flights. Either all the people and goods on the plane have been cleared, or none of them have. But your questions are a good illustration of why preclearance is only allowed on direct flights:

If I am precleared to enter the US (without an immigration check at LAX upon arrival), how will they know that I have been precleared, and they have to treat me differently from other passengers who are not precleared?

There's no way for them to know that, which is why the entire plane must be precleared, or none of it. Some precleared planes even land in airports like New York's La Guardia, where CBP does not process international commercial flights. The first awareness I ever had that preclearance exists came when I noticed an Air Canada flight at La Guardia.

Upon arrival at LAX, there are two kinds of lanes, one for US citizens (and permanent residents), and another lane for non-permanent residents. Now normally I would go to the non-permanent resident lane and would have to go through CBP check. But in this case being pre-cleared, will i be able to enter the citizen lane?

This points out another inconsistency in your thinking: a pre-cleared foreigner is not in the same category as a non-cleared US citizen. The latter must present a passport to a passport inspector, while the former has already done so.

Answer 3

Other answers are correct, but to be concise: Preclearance is not a service that passengers may choose to use, by having purchased a ticket to the United States. Rather, pre-clearance is part of the pre-boarding procedure, precisely for passengers boarding direct flights to the United States from designated pre-clearance facilities. Since all people on such flights (and their baggage) will have been admitted to the United States before boarding, they are generally not subject to border inspection at all when arriving in the United States - the flight is treated as if it is arriving from within the United States.

Airports with Preclearance facilities are listed here, and the vast majority of direct flights from those airports to the United States will use the preclearance facilities. However, even from a departure airport with preclearance facilities, preclearance may sometimes not be employed; passengers on a flight not precleared will then pass through immigration and customs upon arrival in the US.