VIETNAM AIRLINES:

Vietnam Airlines operate flights from Melbourne to Hanoi with the following schedule:

Depart Melbourne: 11:35 AM
Transit in Ho CHi Minh City: 4:20 PM - 6:40 PM
Arrive in Hanoi: 8:40 PM

Total Travel Time: 13 hours and 5 minutes

More information about Vietnam Airlines: 

Vietnam Airlines Baggage Allowance
Vietnam Airlines Meals
Vietnam Airlines Contact

CATHAY PACIFIC AIRWAYS:

Cathay Pacific Airways provide convenient flights from Melbourne to Hanoi with short flight time.

Depart Melbourne: 8:40 AM
Transit in Hong Kong: 3:15 PM - 6 PM
Arrive in Hanoi: 6:55 PM

Total Travel Time: 13 hours and 15 minutes

More information about Cathay Pacific:

Cathay Pacific Airways
Cathay Pacific Baggage Allowance
Cathay Pacific Meals
Cathay Pacific Contact

THAI AIRWAYS:

Thai Airways flights from Melbourne to Hanoi are of high quality service at reasonable price, although they often have an overnight layover in Bangkok. 

Depart Melbourne: 4:00 PM
Transit in Bangkok: 9:30 PM - 7:45 AM
Arrive in Hanoi: 9:35 AM

Total Travel Time: 20 hours and 35 minutes

More information about Thai Airways:

Thai Airways Baggage Allowance
Thai Airways Meals
Thai Airways Contact