Upvote:1
Per the Jetstar website:
For many bookings weβll transfer your bags and you wonβt need to check in again. They include:
- Connecting international flights
Since Auckland-Melbourne and Melbourne-Singapore are both international, your flights qualify: you do not need to recheck bags or pass through immigration, just proceed directly to your connecting flight.
This is presumably the case for your transit in Singapore as well, assuming you've managed to purchase this as a single ticket.