Please book your own international flights. There are a number of different airlines that fly to Nepal and India. If you are flying from the US to Nepal, Thai Airways has good connections via Bangkok. If flying from/Via London to Delhi, British Airways has direct flights.
If Coming to Kathmandu from/Via London, Qatar Airways has the best option. You could also fly with Gulf Air which has good connections.
REMEMBER : Flights get booked up very early especially during the peak months, so the earlier you can make a confirmed booking, the less likelihood of disappointment.