AirBerlin is also worth looking into. I recently booked a flight in business class from Portland, OR to Frankfurt for an incredible $2580, by far the cheapest I'd ever seen from the west coast to Europe in business, just double the $1250 I paid on Lufthansa for economy when I did my ED last year. I'd been thinking of going back this year in September to see the Frankfurt Auto Show, and took the cheap fare as a sign I should go! Interestingly, the flights are all on American (both are in the OneWorld alliance), but the DFW-FRA leg is code-shared as an AB flight. The same exact flights booked on the AA website coded as AA flights were $5900! (also interesting is taking just the DFW-FRA leg without PDX, on either airline, would have been about $2000 more than what I paid!). For some reason, PDX isn't listed on AB's website, so I had to book the flight on a third-party site (Expedia).
Past: 1999 323i, 2003 325iT, 2004 X3, 2007 328i
Present: 2013 335i Sedan, ED Sept. 7, 2012. Imperial Blue/Venetian Beige, no line, Step, ZPP, ZDA, ZDH, ZTP, ZCW, HK.