Air fares vary and the airlines regularly offer trips to promotional price. Current campaigns are presented on the airlines websites. They often last for shorter periods, so quick decisions can pay off. You can find flights at good prices even when there is no specific campaign periods. The challenge is to avoid the times most business travels take place, ie Monday mornings and late nights at the end of the week.
To be out in time, and to be flexible with travel dates, is also a way to book a cheaper trip.
Contact your local travel agent or visit the airline website for up to date information.