Customs and Flight Connection Time

Expect to go through customs the first time your flight lands in the foreign country and the last time you are in a foreign country prior to returning to your home country.

Thus if you are flying an airline with a hub in a certain country, your passport stamps will all be from that country even if you are going elsewhere as your final destination.

My experience with foreign customs has ranged from zero questions asked to a few cursory questions regarding what is the purpose of your visit, how long are you staying, where are you staying, is this your first time here.  It is the same for arrival and departure.

One warning- at Charles de Gaulle near lunch time, my terminal was down to one customs agent.  I had plenty of time for my connecting flight, but others were in a rush.  By being vocal to the agents manning the lines, they were able to cut in front of everyone else.  This is also a good warning that if customs lines are long, it can eat into your flight connection time.  I think I was in that line for a good half hour or so.  You have some but not total control of connection times at the time of your flight purchase.  I have had airlines change connection times on me multiple times especially since I buy my ticket in advance.

For return to the US from Europe:

• The customs process occurred upon arrival at the US airport.  For US citizens meeting certain criteria, the process is sped up a bit if you use an automated kiosk to take your photo and scan your passport in advance of talking to the agent.  Interestingly on my most recent trip, there was seemingly no rationale for who got diverted to the automated kiosk.  I had used it before but got sent to the human attendant line.
• Expect to queue up to talk to a US agent who will ask similar questions as above.   
• Expect to queue up again depending on what you wrote on your customs form regarding whether you have food on you, whether you touched livestock in Europe, etc.  Your bags may need to be scanned and searched to ensure there are not parasites or verboten items entering the US.
• Families travelling together can present together one time to customs; however, make it clear to the agents when you are exiting and he or she collects your form that all members of your group are accounted for.  Otherwise the agent could try to block any laggards from re-entering if they think they are sneaking past without a form.

For return to the US from Montreal, Canada, I found the automated machines at Montreal Trudeau airport to be defunct.  There was something wrong with the receipt scanner in the express machines that everyone flocked to when first arriving to the screening area upstairs.  Luckily there were more machines further along in the airport.  I was also intrigued that the customs process all took place in Canada such that arrival in the US was a breeze.

Thus to sum up- pre flight prep time is minimally different versus a domestic flight for your first departing flight.  Prep time is longer when you first land in the foreign country because of customs.  If you are connecting flights, there is nothing special after clearing customs.  For the trip home, except for Canada, I have experienced customs and concomitant wait times upon arrival home and not at the foreign airports.