The requirement for an open jaw on a paid ticket with most carriers is that the unflown fare component must be shorter than the two flown fare components. (Excepting the rare fare rule that allows a double open jaw, which is what UA's award offers.) Hence why I said in my DL example that ICN-PVG(stop)-BCN-RDU (connections suppressed) would not be legal, as the unflown bit (RDU-ICN) is longer than BCN-RDU. The destination being SFO tightens up the OJ enough to make it legal. For carriers that only offer round trip pricing on awards, this distance rule must be respected to avoid paying way more for the award. With a double open jaw allowed, there is no restriction like this, since it would not be possible to even say what it might mean. AA also does not speak of open jaws on their awards. Everything is a one-way, but you can put more than one on a single ticket, which is helpful if connecting in a region where AA does not allow a connection and requires a fare break (Asia en route to Oz) or to reduce fees if canceling and redepositing.