Flights into Ljubljana and out of Dubrovnik

We're going on the Best of the Adriatic tour in June 2020. It took me a long time to figure out flights. We're flying Boston -> Frankfort -> Ljubljana and then Dubrovnik -> Frankfort -> Boston all on Luftansa.

Originally Frankfort -> Ljubljana was on Adria Airways but Luftansa rebooked us when Adria went under a couple of months ago. Kudos to Luftansa since the original rebook left us with a 5-hour layover in Frankfort arriving in Ljubljana at dinner time and with one phone call and a few minutes of my time I was able to rebook the BOS -> Frankfort flight too so we ended up with a reasonable layover in Frankfort arriving in Ljubljana in the morning.

You might explore flying into Zagreb (2 - 2.5 hours from Ljubljana) or Venice (GoOpti runs shuttles; there may be other shuttle companies).

As for the Dubrovnik end of the tour, if you've got enough time, you could plan to visit a convenient gateway city for a few days and take a budget flight there from Dubrovnik. The Wikipedia page for the Dubrovnik airport lists destinations to which flights are available, though many are "seasonal", and the season probably varies by destination.

Carol - I would go to the individual airports' websites or Wikipedia pages and see which carriers fly in and out of both airports and whether any of those carriers also fly in/out of O'Hare and see if you can get an open jaw ticket, transferring at the airline's European hub. If that doesn't work, check for codeshares with airlines flying in/out of O'Hare that will give you a seamless connection somewhere. There's bound to be something that will work for you.

We did this trip a few years ago and also flew out of Boston thru Frankfurt to Ljubljana and returned Dubrovnik to Frankfurt to Boston. On the return trip we left Dubrovnik later in the day, getting to Frankfurt at 8:30, and stayed overnight at a hotel in the airport. It was actually cheaper, including the hotel stay, to add the next day leg to Boston than to have done it as one trip. This may not be an option flying thru O'Hare but you might check if you haven't already and have the time to return home a day later. We flew Lufthansa open jaw and I did all the booking thru their website.

We flew from Boston to Dubrovnik, via Zurich, on Swissair this past September. We had open jaw tickets, and flew home from Ljubljana to Zurich, on Adria Airways, and then on to Boston via Swissair. I know that Adria has ceased operations. We were probably on one of their last flights. But try Swissair as well as Lufthansa.

Matrix ITA website is my go to flight planner site. You can enter an airport and ask it to search 'nearby' airports and control the distance. Perhaps be flexible with travel dates a well.
Alternatively, Rome2rio may give you some alternate travel logistic options. It is just a first layer look at options, but there might be something that comes up to give you a route we don't know about.
Occasionally, it is cheaper to book two one way tickets, so price those out as well. Generally it is for a trip on different continents (i.e. fly to South America, take a cruise to Europe and fly home - 2 one ways are cheaper).

Bonnie, I'm replying late. Maybe in the past month you've gotten this figured out. We too are taking Best of the Adriatic tour next year, flying out of O'Hare. Our trip is in the fall. I don't have the air booked yet but I'm starting to see some options that look better than what I was first seeing. We're flying from ORD to Venice and spending two nights there, then will use a shared shuttle service to get to Ljubliana. There are lots of choices to get to Venice from O'Hare, including non-stop on American, but the flights home from Dubrovnik using American and its partners are terrible choices. I'm looking for an airline that will get us to Venice quickly at the start of our vacation, then also get us home conveniently from Dubrovnik, so that we can book this on the airline's own website instead of using a third party site like Expedia that puts together open jaw itineraries with multiple arilines. At first it was a frustrating search. I was finding that most flights home involved two stops, or a 10+ hour layover. Now I'm seeing some decent options on Lufthansa and United. For example, there's a United flight that leaves Dubrovnik at 7:25 a.m., has a 3-1/4 hour layover in Frankfurt, then gets to Chicago at 3:05 p.m. On Lufthansa, there's a flight that leaves at 7:25, has a 1-1/4 hour layover in Frankfurt, and gets to Chicago at 1:00 p.m. The routes are good but prices, while not outrageous, are still a little too high for me. So I'm waiting to book. As soon as I see it dip under $900 for our open jaw itinerary, I'll book. I wish Delta and its partners were an option for us, but that appears to be not the case. They don't have flights out of Dubrovnik.

Always worth looking at internal flights in Croatia, they can be quite reasonable on price,

I’m taking this tour in June, leaving from Seattle. I’m flying into Venice and spending a few days there and then taking the Go-Opti shuttle to Lubljiana. At the end of the tour I’m taking a flight from Dubrovnik to Munich, spending sometime there, and then flying home.

I think that pairing with a European city with multiple flights from your point of origin, and then filling in the transport at either end is the way to go.