...Only some legitimate complaints make it to the ACA, but the "service failure rates" of between 10 - 30 major "service failures" per million pax flown (or is it pax sectors flown?) seems low to me, I wonder how it compares to other parts of the service sector or indeed other service industries?
Metro Trains Melbourne had 222 complaints where the Victorian Public Transport Ombudsman approached it (after the traveller had contacted Metro through a government funded call centre, had not been satisfied with the result and then complained to the Ombudsman.) It has about 230 million passenger (journeys) per annum so that's about one complaint per million journeys. However the 'original' number of complaints would be far higher.
Country train and coach operator V/Line (which is government owned) had 105 complaints in 2015-16 that the Ombudsman approached the operator about, but only had about 17 million passenger journys. So that's about six per million trips:
http://www.ptovic.com.au/publications-a-media/annual-reports
One obvious difference is that if a train is cancelled, provided it's a one off and not due to something like a derailment or a suicide, a passenger might only have to wait between three and 40 minutes for the next train depending on time of day, line and day of the week. In contrast only on Sydney - Melbourne - Sydney (and then only QF and VA) do airlines have a half hourly frequency, and even then it's not all day or anything close to it, and nor is it normally more than five days a week.
Another difference is that with surface travel, if a tram or ferry is inoperable, sometimes there's another alternative method such as a train, or a different nearby bus or tram route. With air travel, that is rarely so.
A third difference is that ticketing on airlines is for most of us on cheaper fares completely or relatively inflexible: one is booked on a specific flight and cannot change in many cases without a penalty. For surface travel, a lot is unbooked.
So while comparisons may be difficult (and I'd expect public transport users to be more vociferous than airline passengers), on this basis the airlines may be performing very poorly.