For domestic flights on different airlines where you have to switch terminals, plan for a minimum one hour connection. For international flights where O'Hare is your first port of entry to the US, two hours is safe. How long do I need to leave the airport on a layover at ORD?
Do I have to go through customs for a connecting flight in Chicago?
Arriving at O'Hare International AirportUpon arrival, passengers must exit through the gate at terminal 5 and proceed to the U.S. Customs processing area for a primary inspection. All passengers must proceed to immigration and wait in line after clearing the customs inspection.
Is 45 min layover enough in Ord?
Whatever you do, you're probably smarter not to chance a 45 minute connection at ORD. There's only one direct ORD-CDG connection a day, I imagine if you miss that you'll end up having to transit through LHR (and most likely risk your luggage along the way).