No customs but likely immigration/passport control. You'll get bags in Lisbon. Returning to U.S. you'll need to do customs in your first U.S. arrival city. You should be fine on your connection. What's the carrier? United?
You don't need to go through passport control at LHR for flight connections.
Insufficient information.Before this question can be answered properly,which airline,and is it 1 ticket or 2 separate tickets.
Customs agents are interested in the goods one has. Immigration is interested in the person with the goods.
As above, it's difficult to say how you will connect at LHR; let us know the airlines with which you've booked. An hour is very little time; it's good your bags will be checked through, but there is not a lot of wriggle room for irrops.
You will go through a border exit checkpoint in FRA as that will be your departure point from the Schengen zone.
If on a single ticket you will not go through immigration or customs at Heathrow. Follow the flight connections signs, go through security again and go to your new gate. If you have to change terminals then there is a bus ride before security.
Thank you all for the information. We are traveling on United Airlines; one ticket, with the last segment from LHR to LIS operated by TAP Portugal (but I believe it is still considered a United flight).
Same thing on the return; LIS to Frankfurt operated by TAP Portugal, then United flight from Frankfurt to SFO all on one ticket. I have not gone through Border Control before. Will this take a bit of time? The layover in Frankfurt is also just over an hour.
Your UA flight from SFO to LHR will arrive at T1; TAP fly to and from LIS from T1 as well. You will stay airside at T1; after disembarking from the SFO flight, make your way to Flight Connections. You'll go through a security check (you won't have gone landside since leaving SFO, but it's their house and their rules at LHR) then straight to T1 Departures. At LIS you will go through immigration and customs; unless you have goods to declare, you should choose the blue Arrivals from EU channel in LIS.
I don't know if FRA will include a security checkpoint, but because that's the departure from the Schengen zone your passports will be checked and stamped. Hopefully another AT forum member will know more about the process at FRA and post details of what to expect.
At LIS you will go through immigration and customs; unless you have goods to declare, you should choose the blue Arrivals from EU channel in LIS.
All TravellerPlus posted is correct,except you must not use the Blue EU arrival channel in LIS.In order to use the blue channel,you must have originated in the EU.As you will have originated in the USA,your bags will be tagged with plain white bag tags,so you must use the green or red channels.
Fights originating in the EU have a green stripe on the bag tags,to allow entry to the blue channel.Customs officers watch out for this.
i am travelling to san francisco rom delhi via london and chicago .Where will be my immigartion check at chicago or san francisco