So we are planning a trip to Iceland in August. We have enough points for all of us to fly r/t from here to Chicago on United, but would have to pay for our r/t flights from Chicago to Iceland also on United. How would this work? Would we have to go through check-in again in Chicago? I'm guessing so since I think we'd have to collect our luggage. Anyone have any experience doing in international flight this way?
Yes, my son and I have flown from our city (which is nowhere near a coast or a major airline hub) via American to JFK airport in NYC, and from there, caught a separately booked flight on Air France to Paris, & the same thing on the way home. It was a lot cheaper that way, as the best deals to Europe tend to be from major East coast airports to major European airports, flying on European airlines. Pricing out tickets from my home airport to anywhere in Europe via any airline was really depressing in comparison to pricing out two separate flights with JFK as the hub.
On the way out, we took an early morning nonstop flight from our home airport to JFK, then caught an afternoon flight from JFK to Europe, so there were several hours of cushion time built in just in case the first flight was significantly delayed. (If you do this, be sure to leave on an early morning flight which are the most likely flights to leave on time, and don't take a flight with any stops). Yes, we had to pick up our luggage in JFK & go through security again for the international flight. Build in plenty of time for that (although in our case it didn't actually take very long), and again, build in time for delays. Also make sure that your absolute necessities for the trip & a few changes of clothes are in your carry-on bag, just in case your check-in bag doesn't make it.
On the way home, we flew to NYC from Europe and spent the night in a hotel connected to the JFK airport, and then flew home the next morning.
Obviously, this type of travel isn't for worrywarts, and plenty of posters might try to dissuade you from it. If you exercise caution in your flight type & times & luggage, and have a fair amount of tolerance for risk, it can work out very well. I liked the very substantial savings we got.