Check again, "Future_747_f/o",
From UA's timetable alone (other sources could confirm this):
UA 815, LAX-SYD, 7487 miles, 14:25
UA 895, ORD-HKG, 7793 miles, 15:55
UA 847, LAX-MEL, 7920 miles, 15:20
Don't have the stats for SA's flight from JFK to JNB but I believe it falls somewhere in between UA 895 and UA 847 where *distance* is concerned, not sure about total time elapsed.