This Druk Air flight from Bangkok to Paro, through Kolkata, leaves super early, depending on the season. For me, it was 5 am, which is a tough schedule. But it gets you into Paro early in the morning, which has some advantages.
Flying into Paro is always fun, with so many twists and turns through the tight valleys. It's certainly one of the most exciting landings for any airport. Be sure to book seats on the left side of the plane if you can, so you can get a great view of the Himalayas on the way in.
The food was decent, but the coffee was bad. Stick to water. Service was pleasant and friendly.