Only citizens of India, Bangladesh and Maldives can travel to Bhutan without buying a package tour. The rest of us need to reserve and pay a package tour from a Bhutanese travel agency after which one gets a visa and is issued air tickets. Tours are not cheap (200-250USD per day) but include hotels, full board and transportation with a guide and a driver (both expect a generous tip afterwards). Its all very well organised, but it is also worrying to pay all in front and only get copies of visa approval and plane tickets by email. Visa will be stamped when arriving and there little fuzz about it at Paro airport.
Almost all tourists enter Bhutan by air. There is possibility to travel by bus/car from/to India (Assam or Sikkim), but it takes a lot of time. Landing and taking off in Paro airport are an experience. The short runway in a deep valley requires specially trained pilots and planes have to weave through hills to land safely. Only two airlines have regular flights to Paro – national carrier Druk Air and newly established private Bhutan Airlines. Druk Air does good job and I felt quite safe and happy in their hands.
Flying to Bhutan is spectacular also as one can see Himalayas especially when flying from New Delhi or Kathmandu. Below a picture of probably Mt. Everest.
Paro airport is small but efficient. There was a quick queue to get your visa stamp and then short wait for baggage. Arriving tourists were greeted by pictures of old and new king (father and son) and also big poster of the King and Queen.