The delayed QF1 took off from DRW at 2342 hours on Thursday 23 December with expected arrival at LHR becoming 0631, 86 minutes late on Friday 24. This gives more than three hours for the aircraft to be prepared for QF2, the 0950 hours back down to DRW and SYD.
Also yesterday, QF2 (B789 VH-ZNJ) was airborne from LHR at 1013 but is not predicted to arrive in DRW until 1247, 62 minutes behind, so arrival in SYD tonight will be at least half an hour late.
QF9, the Thursday 23 1845 hours MEL - DRW - LHR (B789 VH-ZNC) did not take off until 2152, arriving DRW at 0014 on Friday 24 (169 minutes tardy). It then became airborne at 0152 with claimed LHR arrival on the dot of 0900 hours, 130 minutes behind schedule. If it forms QF10, the 1120 hours LHR - DRW - MEL it should be able to depart at or close to time.
It's unclear why QF9 was delayed given that ZNC had been in Melbourne all day yesterday from 0831 hours, having arrived on QF94 ex LAX 36 minutes late.