Booking discount air travel can be hit-or-miss. Either you hit that one deal or you miss out on a low fare altogether. Blink at your computer screen, and the $79 special between Los Angeles and Denver might be gone. So what can you do to beat the fickle airlines and secure the best deal? According to some travel experts, the day of the week that you book your airfare is important. As with gas prices, airfare almost always goes up on weekends. Mid-week, however, after major airlines release new sales and other airlines match the lower prices, can be advantageous. Monday may be too early to capitalize on the lowest prices, and Thursday may be too late. Tuesday evenings and early Wednesday mornings are generally the best windows in which…