From Bagdogra airport via Manebhanjan you can reach Sandakphu Phaldut. You need to do an over night stay in Manebhanjan and then travel to Sandakphu which is 2 hours away. Another route is via Mirik from NJP which is 4 hours away from Bagdogra and 2 hours away is Sandakphu Phalut. It is better to travel by keeps or Land Rover.