I will go to Cairns, Australia for a meeting later and fly back to Hong Kong at 5: 30 in the morning. How can I get to Cairns Airport from the hotel so early?

Don't worry too much. You stay in a hotel at night, right?

You can tell the hotel in advance what time your plane will arrive at the airport in the morning and ask them to refuel you.

Last time I was in a situation similar to yours, I flew from Cairns to Brisbane at 5 am.

Another is that you can call the hotel front desk to make an appointment yourself. There is a local telephone dedicated to booking taxis.

Then call that number yourself to make an appointment, and the price is the same as the normal taxi fare.

Anyway, in a city as big as Cairns, don't worry about the driver saying you.