Most places in the country are well connected by roads. We have our own luxury buses, and other means of transport can be easily arranged.
There are only two entry points to Bhutan. While most travelers arrive by air at Paro (The only International Airport in Bhutan), some arrive by road at Phuntsholing, which lies on the southern border with India.
In either case, tourists have to fly in/out by the only national carrier, Druk Air. Druk Air has no interline agreements with other carriers. Hence, tourists need to arrange for their own tickets to and from wherever they connect with Druk Air, as that is the only airline that flies into Bhutan. Flights from Kathmandu to Paro provides the most spectacular view of Himalayan vistas of any scheduled flight. Druk Air does not issue tickets until they have received the visa clearance. Paro airport is just a drive of 1 hours 20 minutes from Thimphu.
One good news for the travelers these days is, they have an option to fly from Kathmandu using another carrier, i.e., Buddha Air a Nepal based Airline.