Best and fast way from Argyle street/ Nathan Rd to Hong Kong airport

Oh, according to the departure time, you are suggested to arrive at the airport at around 08:00.
You can take direct shuttle bus no.A21 at Mong Kok Market, Argyle Street. The duration is about 50 mins. It costs 33 HKD per person. You'd better take the earliest bus scheduled at 05:30.
Or the fastest way is to take a taxi directly. The fare is 310 HKD to 320 HKD. It takes around 30 to 35 mins on the way.
You can choose the way you like. :)