What can I do if an airline cancels my return flight?

What can I do if an airline cancels my return flight?

They will have to protect the rest of your itinerary so that you can complete your journey. It's their legal obligation as part of their contract to fly you (you entered into a contract with them when they sold you a ticket), if you choose the take up the alternative flights. If you don't, then the compensation varies from the type of ticket you have and type of carrier you're ticketed with. Call them up to make new arrangements.

What was the cause of the flight cancellation?

They have cancelled the flight. Offered me a flight the next day but I was to be responsible for hotel etc for the overnight stay and visa extention fee.

It was a business class fare from CDG to MEL via SGN and the leg from SGN to MEL was cancelled.

Delayed, not cancelled will be thier first Argument. Who was the airline, if its an EU based Airline, you are eligable for a minimum 600 Euro compensation, on top of what ever you can get back from them to cover bills.

Not sure if any of this applies to Vietnam Airlines...