Open jaw simply means flying into one city and flying out of another. I've often found that for AA flying into London and home from Paris for example may be no more costly that round trip to and from either location. With my free business class award, however, in addition to the open jaw, I'm allowed one stopover each way, or a stop-over and a gateway city stop-over going one way. But those opportunities don't usually exist with booking of a coach class ticket.

Technically last year my itinerary was flying from Ft. Lauderdale to Berlin with a long stopover in New York (gateway city) and another in London. Then I flew home direct from Paris to Miami. (They even consider leaving from Ft. Lauderdale and arriving back at Miami the same origin point.

Thanks Patrick. That's very helpful!