Flying from Lisbon to PHL and then connecting to flight to Chicago. When we arrive at PHL , I think into Terminal A, we will have to go through immigration, collect our luggage and recheck it to Chicago and then must get to gate in terminal C. All flights are on American. How do we do this? Can we walk between terminals or must we take a shuttle? Must we go through security again in Terminal C? We have 1 hour and 50 minutes until the connecting flight. From past flights it looks like the LIS to PHL arrives in terminal A and the onward flight leaves fro Terminal C. Please advise the best, fastest and most efficient way to do this. This is a Sunday afternoon flight so I think it may be crowded.

You can walk from C to A in about 10 minutes. No issues. You will not need to go through security again.

What is your concern about it being Sunday and flights full? I see no reason why a Sunday flight would be fuller than a weekday when there is more business travel, but how full a flight is should not be a concern one way or another.

If your arrival is on time you should be absolutely fine. If your LIS > PHL flight is delayed (assuming it is all on one AA booking) they will put you on the next available flight.

By any chance do you have Global Entry?

Yes we both have global entry. And Yes my Chicago flight is a connection on the same ticket as international portion. I have just experienced very long delays in getting luggage at the international terminal at ORD but have not experienced a connection through PHL and am relying on those of you have experience at PHL. Is the shuttle an option if we are running late or is it actually faster to walk to other terminal?

no shuttle. You can walk from C to A in about 10 minutes