So what about passengers who plan in advance or wait until the last minute? Well, if you know where you're headed 225 days from now you should probably inject more spontaneity into your life, but short of that -- by all means, resist the urge to book it! That's the date when fares start to decline ahead of a flight, falling slowly until day 54 before beginning to climb again.
As for those who lollygag and then complain to friends about how expensive it was to book a flight to Coachella, like, three days before Coachella, no real shockers here. True to form, tickets are at their most expensive the day before a flight; and second-most costly two days prior.