flight time Frankfurt to chicago

We left from NC to go to Frankfort Germany. We had to change planes in Atlanta Ga and the flight was 10 hours
If you're flying nonstop, then the flight is a little over 8 hours from Chicago to Frankfurt - about 9 hours returning from Frankfurt to Chicago. (It always takes longer from Europe to North America because of the headwinds).
depending which nonstop flight you choose. This is O'Hare *to* Frankfurt. Fastest scheduled is Lufthansa flight 431; slowest is American flight 84. United, Lufthansa, and Air India have other nonstop flights on this route between 8h, 15m and 8h, 30m.