Bhutan has limited domestic air services. Airports have been developed in Yongphula (south of Trashigang in the far east), Gelephu (in southern Bhutan, near the border with India) and Bathpalathang/Jakar (Bumthang, central Bhutan). At the time of writing, only Druk Air had scheduled domestic flights from Paro to Bathpalathang (via Gelephu fortnightly). Check with your tour company to see the current status.
The Royal Bhutan Helicopter Service operates charter flights, sightseeing and medical evacuations from its base in Paro.