Pre-Sars, CX had five NRT-HKG, which is now slashed to one. CX added a mid-afternoon flight around this time last year.
Of the five, F was guaranteed on the last two flights of the day in the evening, both 747. The last one is nonstop to HKG while the other was via TPE.
The other three were two in the morning, both nonstop to HKG and another in the midafternoon, also nonstop.
The two morning flights were the ones that arrived from HKG the previous day in the evening (afternoon flights) and stayed overnight. They are often 777 and short-range Airbus.
However, quite often, one of the two morning flights had F.
When it started, the midafternoon flight was served by 34C (with New Business Class), meaning F was there. But the equipment was later often replaced by 777 and short-range Airbus.