What's out: Peak-time air travel. What's in: Off-hours air travel.

For years, the airlines' best deals came with an annoying catch: You had to stay in your destination for at least one Saturday night. The Saturday-stay hitch has been greatly eroded by the market pressure applied by the no-frills airlines. Those upstarts also made one-way tickets affordable, which the legacy carriers have learned to imitate. Back in the day, the major airlines skinned you alive if you only wanted to fly one-way.

But one elementary loophole of airline pricing remains, and it can still be exploited. That rule is simple because it's rooted in basic economics: Fly when fewer people want to. It's simple supply and demand, really. When flights fill, prices escalate. When seats are empty, prices stay low. If you have ever purchased holiday flights many months in advance, it's because you already live by this rule.

Now that airlines are bleeding us for every little thing from checked baggage to water, it's more important than ever that we exploit every angle in keeping our money in our wallets and out of their clutches. When you're paying for your own ticket, gone are the days when you'd blindly purchase any seat on any flight. Now, you scrutinize the schedule for the lowest airfare, because that $30 you save can now go to the cost of checking your bags.

Just think of all the reasons that flying in the off-hours makes good sense: