It re-starts in June and runs until the middle of August. Not daily, so check bracketing days. You appear to be assuming you're using it, however, as it's the only eligible flight between YVR and SFO. Most west coast North-South flights shown in the OW timetable are on Alaska Airlines metal, ineligble for the OWE. The YVR-SYD flight stops in SFO without changing flight number. And there is no SFO-DTW flight that I can see.