Ticketing and reservations are not restricted to just air travel but are a big part of railways and the bus transport too. The basic responsibility of a ticket agent is to sell tickets and provide the passenger with all the information that he requires for his trip. This would include the availability of tickets, flight/train/bus schedules, seating arrangements etc. Most of the travel & ticketing courses are provided at the postgraduate degree and diploma levels.
Useful Information on Travel & Ticketing