Travel enthusiasts seem to be consistently split on whether booking a flight at the last minute is generally cheaper than booking in advance.
The reality is that buying a ticket in the hours or days before the flight's departure can potentially reward you with a discount but so can planning ahead and purchasing your flight months before. It all comes down to how crowded the flight is, what time of year it's flying, and when in the week the plane departs.
Sometimes last-minute is cheaper, sometimes it's not.
The key is to frequently compare ticket prices and to keep an eye out for any promotional campaign or slow, off-peak period deals. Last-minute flights can be cheaper but they aren't always.