The Rick Steves trip we are taking ends in Vienna, we will have already traveled a week before the trip. Looks like flights from Vienna are a little more costly. With a reasonable trian ride where else could we fly
out of back to SFO that might save flight funds?
Munich is generally cheaper to fly out of to the U.S. than most continental airports. With advance purchase (3-92 days, the more, the better), you can get rail connections from Vienna to Munich Hbf for as little as €29. Use the German Rail website to find Savings Fares.
You might try Zurich. It has worked for me 2X and I obtained a great fare also. Ttrain stops at Zurich International Airport also.
A lot of people suggest Bratislava airport in Slovakia for cheaper flights, but the direct bus takes 2 hours, which is a bit far for me.
I suggest Bratislava or Budapest. Or if you can find a cheap flight from London or Paris or another city, you could take a cheap intra-Europe airline from Vienna to the other airport.
The closest airport from Vienna besides Schwechat is Bratislava (about 1 hour by train or bus). Second closest is Brno where you can catch Ryan Air to London and by summer also flight to Eindhoven (close to Amsterdam). Brno is about 2 hours by train or bus. Budapest and Prague are further away (3-4 hours resp.).