This question already has an answer here:
This January my family and I are returning to the UK from a holiday in Australia. The ticket is booked from Canberra to LHR via Sydney and Doha with Qatar, flight 907 I believe.
Because we're finishing our holiday in Sydney (we start in Canberra), we were hoping to simply join the flight in Sydney, and avoid a 3 hour drive to Canberra, followed by an extra leg back to Sydney.
We contacted the travel agent (Expedia) to confirm if this was possible, and they said the Sydney stop is refuelling only, and we can't board there. Is that really the case? Would it be worth contacting the airline directly to confirm one way or the other?