Advice for flying out of Dublin to the States!!!

So, I didn't know this and didn't find out until it was too late so I figured I'd pass this info along to anyone who might be flying out of Dublin back to the States.  In the airport you go through regular security as usual, but when you get to the terminal for flights to the US there are two checkpoints to go through.  The first is where you fill out the blue form declaring your customs information and the second is the actual passport checkpoint.  Once you're past the passport control point, you CANNOT leave the terminal unless they cancel your flight!  You've already been processed as having entered the USA even though you're still in the airport.  There isn't an ATM machine, but there are a couple of vending machines and a small restaurant.  So to prevent yourself from being trapped (for lack of a better word), don't go through until you absolutely have to!!!

My experience has been that this only applies to Aer Lingus and American Airlines flights. The last time I flew Aer Lingus to San Francisco, I went through customs in San Francisco and not in Dublin.

I just flew from Dublin to JFK on Sunday on Aer Lingus and also had a slightly different experience than the OP.  We connected to Dublin from Edinburgh, so that may have had something to do with it - not really sure.  Either way, we flew into Dublin and then passed through Irish immigration control, where my passport was stamped and the IO hand-wrote in "I.T.", presumably for in-transit.  We walked over to the terminal for our US flight, where we passed through security again, but we never received the blue US customs form, and definitely were not stamped into the US.  I do remember noticing that most of the other passengers on our flight already had the customs form, and I was wondering why we never got one.  Once we arrived at JFK, we went through US immigration and customs as normal.

Perhaps it's different if you don't arrive in Dublin via a connecting flight, but I found the whole process to be pretty standard.  (Except the part where I was mocked by the security agent for forgetting that I had bought a bottle of whisky at the duty-free shop, but that's a whole different story...  )

That's funny because the last time I flew to Dulles from Dublin (on Aer Lingus) this summer, we didn't go through customs in Dublin and we ALWAYS did this in the past. I even mentioned it to my husband later how I thought this was strange.

Honestly, there's no rhyme or reason to how they do ANYTHING in Ireland! 

I think that going through customs in Dublin varies depending on your destination. When I've flown to Chicago - went through customs & immigration(aer lingus), flew to San Francisco, (also aer lingus) did customs and immigration in SFO. It's actually quite nice getting it done before you get on the plane.

On an additional note: if you fly to the US through Vancouver, BC on Air Canada -you will go through customs in Vancouver before boarding your connecting flight. I've found this to be very quick and easy!