Domestic air tickets and International air tickets for flight reservation online can be done at Yatra by paying lowest airfare.
Websites of several websites are listed here. But you cannot say if a particular airline always offers low priced tickets.
So we recommend to use Booking Engine provided by yatra where you can compare prices of several flights, also check which flight has less duration of journey, any stops enroute, etc.
You can book tikets online at yatra for Indian Flights, International Flights and Hotels in India.
Wanna Fly Cheap? Go to FlyCh.com , AirDeccan.ind.in
Travel Package? Go to FlightHotelHoliday.com