I was wondering if anyone knows if one goes through American Customs and Immigration when leaving Cancun? I experienced that when I was returning home from the Canadian Rockies and it made for much faster connections once in the US.

Cancun is not one of the places that you can preclear US Customs.

Here is a list of where you can - mainly but not exclusively Canadian locations.
http://www.cbp.gov/xp/cgov/toolbox/c..._locations.xml

So you will have to deal with that at the first place you land in the states. The airlines official minimum connecting times have this factored in.

raquel

Raquel_z that's an interesting list, I didn't know preclearance existed anywhere but Canada.

Thanks, Raquel, for your response and for the interesting list. I never would have imagined that Europe would have any places where one could clear American customs and immigration. I am still a bit concerned about my one hour and ten minutes connection time. But then, I have missed many connections in my lifetime and am none the worse for them.

I too was surprised to see Ireland on the list. I haven't flown from there to the US - so have no personal experience. I did fly from Nassau to the US years back and did preclear.

Whether you make your connection or not will of course depend o what airport you are flying into and how many other planes have landed at the same time and where yours ends up in the mix.
If the airline sold it to you as a legal connection, they expect it to normally be adequate time. However, flight delays happen and that will set it all off..
Good luck
raquel