AirBerlin is a OneWorld alliance member, so you can use American Airlines AAdvantage miles to book trips on it.
My family flew open-jaw in Coach last Fall to Venice, returning from Barcelona, on a combination of AA and AB.
Now AirBerlin is adding more trans-Atlantic flights, which is a good thing.
As a tall passenger, my favorite feature of AirBerlin is the (extra-cost) availability of their XL (extra legroom) seats in Coach. But you have to be vigilant…weeks after we were ticketed, they did a schedule change and put me into a standard seat. A phone call to their courteous call-center man got that rectified, but it was just luck that I noticed the seat change.