British Airways and Lufthansa have round-trip flights from Austin (AUS) to Dusseldorf (DUS/QDU) for $528-$606 with a connection. Lufthansa offers a Flight+Train option (see note). Flights March, April, May, and November. No Friday or Saturday departures. 7-day minimum stay required. No Thanksgiving dates.
Read this note: If you’re flying Lufthansa you have the option to buy a fare that allows your connection out of Frankfurt to be on Train via Deutsche Bahn to (QDU) Düsseldorf Main Station (the train station). This is usually cheaper and faster than taking a flight from FRA to DUS. If the logistics are to confusing, just pay more for the British Airways fares that connect in London.
Flight+Train users: When you land in Frankfurt, You‘ll get your luggage right in front of Frankfurt Airport Station at the train station pick-up point, not the regular carousels.
Expedia often has hidden discounts for logged in users. In this case it was -$16.35 off, but it can vary. Be sure to log into Expedia while searching. See screenshot for an example of what I’m talking about.
Click for more details and booking links Cheap Flights: Austin to Dusseldorf $528-$606 round-trip (Flight + Train option available) [Mar-May, Nov] – British Airways / Lufthansa / Expedia