Had a question on what - if any - slack Cathay has in its system.

I was on CX872 last night, which took a nearly two hour delay because of what staff thought was a mechanical problem with its right engine that held it up at its previous port of call, Manila. The flight came on board the displays an hour down, and once it arrived, maintenance crews there opened the right engine cowling and started shining lights. The delay then stretched to 100 minutes. The gate agents offered little information, saying that an engineer had to inspect the engine, but that they were not going to cancel the flight.

They soon did an engine run up at the gate and apparently seemed satisfied with the results as they called everyone to board. We got the op-up, thank goodness. We ended up down 2 1/2 hours, making up no time enroute due to unfavorable winds. I wasn't too bothered by that because I never schedule anything right at the end of a long haul trip anyway, and the op-up always helps , but I was curious as to the availability of spare planes.

The plane that operated this flight, B-KQM, is a 13-month old 77H according to FlyerGuide and Airfleets, one of 33. Is it plausible that Cathay is running all 33 77H in a single day? I noticed this bird had been running around South Asia all day, to Beijing and Manila, after running a TPAC from LA the previous night. Is this a typical cycle? Are Cathay less willing to cancel simply because they have no spare birds, or is it something else? They really seemed intent on having that plane do the SFO run that night...there was never talk of canceling or getting another bird to do the flight.

CX is really running to capacity in the last few months, with favourable exchange rates for outbound travel and low fuel costs.

I think it'll really hate to do 26 hours of rescheduling. Particularly since the problem can be managed, as your eventual result show.

I think overnight is the hours that CX has the smallest number of 77Ws in HKG comparing to other hours in a day mainly because most long haul departs at around midnight and those Europe arrivals (excluding LHR) returns at around 5-6am.

Just counted - there are 12 x 77Ws departure at 23:00 - 01:00. And 17 x 77Ws arrivals at 05:00-07:30

particularly what LchChester says above.

A huge amount - the overwhelming majority - of 77W long-haul arrivals are early morning. Then, a few more long-haul arrivals trickle in throughout the day. A few more long-haul departures trickle out throughout the daytime. Departures pick up a little in the early evening. Until finally, late night, there is another huge slam of 77W departures within a few hours.

Because the majority of long-haul missions don't depart until late night, there is quite a bit of "slack" in the early morning, ebbing and flowing throughout the day, and finally it gets pulled tight late night. Hence, during the daytime CX tries to deploy the 77Ws around Asia to keep the frames utilized, and tech issues in those outports could have a knock-on effect for the late-night departures because that's when slack is the tightest.

CX's 77Ws departing HKG late night (some depending on day of week, I actually counted 13)

LHR (x2)
SFO
LAX
YVR/JFK (CX888)
FRA
MXP
FCO
AMS
ZRH
CDG
JNB
MAN