Bhutan has no railways; travel is by air and road. The only international airport is Paro (PBH), served by Druk Air and Bhutan Airlines with connections to Delhi, Kathmandu, Bangkok, Kolkata, Dhaka, Dubai and Singapore. Flights are daylight-only and weather-dependent (allow extra time for transfers). Overland access is only via India: the main border crossing is Phuntsholing (west) and another at Samdrup Jongkhar (east). Buses and taxis run from Indian cities (e.g. Delhi/Guwahati to Phuntsholing) but a valid Bhutan visa/permit is required before boarding.
Once inside Bhutan, most visitors travel by private vehicle with driver (usually arranged through your tour package). Bhutan has limited domestic flights (to Bumthang, Gelephu, and Yonphula) but they are infrequent and weather-sensitive. The rugged mountains make road travel slow; a short journey may take half a day. State-run intercity buses connect major towns (e.g. Thimphu–Paro, Thimphu–Punakha), but schedules are infrequent and buses can be crowded. In cities (Thimphu, Paro) yellow taxis are available (note: fares are negotiated, not metered). Visitors may also rent cars or bikes in Thimphu, but driving is challenging due to narrow, winding mountain roads.