To the above, the rego's being in in advance do serve the curious among us, confirming the jigsaw puzzles I construct in my mind!
-XFE was late leaving MEL this morning as VA87 to HKG. It arrived on time ex-HKG as VA86 on Friday morning, so presumably something went tech. It departed at 12:08, arriving 19:49 in lieu of a scheduled 17:40.
VA86 on Friday evening, a scheduled 19:50 departure, turned to depart at 22:20, and is due in to Melbourne at 09:30ish, in lieu of a 07:20 arrival.
Virgin Australia has a relatively small fleet of A330s, but Hong Kong is an ideal destination for them as they can turn one aircraft around each day in each port, thereby providing a daily service using only one frame. However, where this comes unstuck is if a significant delay comes in. As there is an allotted turnaround of 2hrs 40mins in MEL and 2hrs 10mins in HKG, it's very difficult to catch up more than an hours lost time within 24 hours. Especially so in two rather constrained airports.
Indeed, trying to catch up over 2 hours lost time would require some extremely fancy footwork. You'd probably never get it done, truth be told. Normally this would require a substitution on the domestic network for at least two sectors, as an A330 is pulled from transcon and picks up the slack to HKG. This frame could then continue the HKG rotation per normal, or they could choose to return the original A330 the following day, after sitting on the ground (or a return PER, if the tech issue fixed in time).
All that said, if ever there was a day when you would want something like this to happen, it's Friday. This is because Saturday is normally a day off for the A330s (excluding peak times when NAN is A330), as they are surplus to demand. Given a return HKG trip is timetabled at 21hrs 20mins from off blocks to on ground, it can be departing for PER (or wherever else) by around 10:30 following arriving from HKG.
I can't say for sure if a transcon flight tomorrow or early Sunday was or wasn't downgraded, but by the time -XFE lands in MEL on Saturday, -XFH should be close enough to fully boarded and ready to go to HKG. -XFE will then reappear on Sunday morning's VA87, while -XFH does a SYD return on Sunday afternoon following it's arrival from HKG, and then jets off across to PER.