On the OTP comparison with Jetstar, I have noticed that if a jetstar flight is running an hour or so late they reschedule the flight, does that then mean that it can leave 'on time' based on the new departure time?
Correct! So, as an analogy - JQ 666 is running 3 hours off schedule, it's scheduled time of departure was 1345. They cancel the flight altogether, create a new flight number - JQ 667 with an ETD of 1645. Guess what, it is actually off blocks early at 1642!!!! A miracle! Old flight cancelled, new flight created and departs on time.........oldest trick in the book. Welcome to aviation smoke and mirrors lesson 1. Lesson 2 is 'how to fudge ACARS'
....TBC