Adriatic tour: Best connections: US (Washington DC) to Ljubljana

Unfortunately, Washington, DC is not one of the places budget airlines fly to.

You could run over to Baltimore and fly on WOW Airlines through Iceland into London Gatwick. From there, you can fly non-stop into Ljubljana very inexpensively on EasyJet.com--a big budget airline. Just travel with a light load and be aware of the terms on any budget airline.
When I start looking for flights, I go through http://matrix.itasoftware.com/ I'll also go to Wikipedia.com for the city I'm visiting to see where flights go to non-stop from their local airport.

I make no promises, but try Zagreb (quick trip to Ljubljana), Munich (probably your best shot if you don't want to fly the leg to Ljubljana), Venice (but beware crack-of-dawn departure times for the return trip), Milan, and Vienna. Maybe also Budapest since James E has reported a plethora of low-cost intra-European flights from that airport.

I'm all about limiting flights to as few as possible. When my daughter was headed this way from DC, I booked her on the Philadelphia to Venice nonstop. You could then bus to Ljubljana in just over 2 hours. It was a USAIr flight when she flew it but I guess it's an American flight now.

Look into flying to Venice or Munich, there are usually much better and cheaper connections than into Ljubljana. From Venice, it's a two hour shuttle transfer to Ljubljana or a train to Trieste followed by a bus to Ljubljana, all on the same train ticket. From Munich, it's a 6-hour train ride through the Alps.

Listen to Dejan; the van to Ljubljana leaves right outside the Venice Terminal, around noon, and drops you at the Ljubljana train station; return is the reverse .

Austrian flies direct from IAD to Vienna. From Vienna to Ljubljana it is a six hour train ride and should cost 29 Euro online in advance for a specific train.