There can be many variants. Especially when it comes to international ticket sales. Airlines usually like to have a particular percentage of seats sold by a certain date on international, sometimes when there is a lull in sales the airline may quickly release 50 tickets per flight say on two weeks of flights for quick sale, and this is when the real savings are to be had. It happens over here in Australia alot and you can save up to 60% on a flight. You usually have to pay for these tickets immediately or within 3 days and that does depend on the airline company.
