score:6
You've got so much time between your flights that you're likely to spend almost the entire time bored out of your mind.
Your PIT-ORD segment historically arrives early, even when it leaves late, because it's scheduled as a 2 hour flight but actually takes about 1:15. So, you'll generally arrive in Chicago around (or even well before) 9:00 am for your 1:05 pm departure. You'll find yourself with a four hour layover.
And all you have to do in Chicago is make your way from Terminal 3 to Terminal 5 on the ATS train. If you didn't get your ORD-AUH boarding pass in Pittsburgh, pick it up here. Then go through security, and wait several hours for your flight.
In particular, you should be aware that the US does not have exit immigration controls. Your passport will not be stamped. Instead, the airline will inform the US when you have departed on your plane.
Upvote:1
There is no difference between a domestic-to-domestic transfer and a domestic-to-international transfer in the US. The US has no exit checks. Someone leaving the US (no matter American or foreigner) does not "get stamped" or otherwise get any checks from the government.
In the US, there is no difference procedurally between international departures and domestic departures. That means you don't necessarily "switch terminals" or "collect baggage" or go through any "checks". In particular, I've personally done a domestic-to-international transfer at ORD by simply walking down the terminal from one gate to another. It's exactly just the same as transferring to a domestic flight except for the location written on the destination sign. (Well, my transfer was from United to United, so it was natural it was in the same terminal. It's entirely possible for your transfer to be to a different terminal, especially if you are transferring to a different airline, but it has nothing to do with whether your second flight is domestic or international.) If it's on the same ticket, the baggage will almost certainly automatically transfer over, no matter if you have to change terminals or not.
You haven't given enough information to determine what terminals you will go through. In particular, Etihad doesn't serve Pittsburgh, so at least the first flight is operated by a different airline (probably American Eagle, Frontier, or United). Assuming that your second flight is operated by Etihad, Etihad does depart from Terminal 5 (the "international" terminal) at ORD. The first flight will probably go to a terminal other than 5 (e.g. American Eagle and Frontier use Terminal 3, United uses Terminals 1 and 2), so you will probably have to change terminals. It doesn't seem like there's any after-security transfer between Terminal 5 and other terminals at ORD, so it seems like you would have to go through security again. I think 3 hours is probably sufficient, but that is just me.