Druk Air (Royal Bhutan Airlines) is the main air carrier in and out of Bhutan. Daily air services between Paro and Bangkok are also operated by Tashi Air (Bhutan Airlines), an independent Bhutanese airline. An internal flight operated by Druk Air flies between Paro and Bumthang. Flights can be subject to disruption due to weather conditions.
Phuntsholing, Gelephu and Samdrup Jongkhar in eastern Bhutan are the only land border areas open for international tourists. You can get more information on the Tourism Council of Bhutan website.
The nearest British consular office is the British Deputy High Commission in Kolkata, which should be your first point of contact for consular assistance.