I live in Asia and you never know for sure, it wouldn’t hurt to check the website before you buy at a ticket office. It depends on the airline, where you’re going and the seat availability on the particular flight you want. For most of the budget airlines here, you can buy a last minute ticket for a pretty good fare, and some of the major airlines also will discount fares when they know the flight won’t be full for last-minute travel. But like almost everywhere, advance purchase is usally the best way to go.