For direct flights, about 9.75 hours flying time.
Delta airlines claims about 52 hours, which I think is too much, You should check your local airlines' website.
five hour flying from sydney to Tonga
Sydney is four hours ahead of Hanoi from early October until early April and three hours ahead from early April until early October.
The flying time from Sydney to Adelaide is between 09:00 and 16:00 depending with the day.
For direct flights, about 1.5 hours flying time.
For direct flights, about 21 hours flying time.
Nine o'clock in the morning.
9 hours
About 18 hours.
14:58
The flight time from Sydney, Australia to Laos is about 9 hours, 23 minutes.
8 hours