Quickest way from Kunming North Bus Station to Airport

I shall arrive to North Bus Station at about 3 PM and I shall have to get to the airport as soon as possible. Please let me know, which is the quickest way to the airport: to take the metro and change two times or to take a taxi? As far as I know, airport shuttle No.3 does not start from the bus station.
How long will it take approximately?
Thank you for your help.
Eni