Newsflash: Flying isn t cheap.

As airlines have come under greater pressure from elevated fuel prices and a decline in travel demand, many have rolled out new fees that only begin when you purchase your ticket. Depending on your carrier, bags, leg room and even pretzels could cost you a premium.

Their most lucrative area, business travel, was hit hard -- instead of cutting people, businesses cut travel, says Rick Seaney, CEO of FareCompare.com, an airfare comparison shopping site. They re having to figure out other ways to make up shortfalls in revenue.

Although you might feel nickel-and-dimed, roughly 20% of all flights would have empty seats if the carriers didn t discount, Seaney says. That means there are opportunities for savvy shoppers. The key to saving on air travel is to understand a few basic rules.

Timing matters

Over the last year, a pricing pattern has emerged. An airline sets up sales on Monday night, and everyone else matches the price on Tuesday, says Seaney. The sales are typically yanked on Thursday nights, so that gives you three days to take advantage. If you re shopping on the weekend, you re paying too much, he says.

Also, most people think buying far in advance is a better deal, but that s not the case. When you re buying domestic air travel, you don t want to buy much further out than three months, or you ll be paying more than you should, Seaney says. But you must buy outside of 14 days to departure. Once you re in the fourteen-day zone, you start be treated like a business traveler with a bigger wallet, he says.

The days you travel on matter, too. Tuesday, Wednesday and Saturday are the cheapest, so if you can structure you re trip around those days, you ll save. Flying on peak travel days (Monday, Friday and Sunday) can cost you $10 to $30 more.

Use your head -- and your points

More consumers are turning their rewards miles into coupons, says Randy Peterson, the founder of FlyerTalk.com, an online frequent-flier community. They are using them for incremental savings, instead of amassing the number of points they d need for a free ticket.

If you only had three hundred or so, you were out of luck in the old days, because you didn t have enough points for a reward, says Peterson. But United and Delta (if you re a credit card holder) will allow you to use your miles as a discount against your normal fares, he says. Most people don t really read much about their frequent-flier programs and don t realize what the airlines are doing, says Peterson. Miles are becoming the new discount code/coupon.

Using miles as coupons typically releases the buyer from restrictions on the destination and trip date. They work, more or less, like cash.

The key is that you must purchase the tickets on the airline s web site not a third-party booking site. Generally, airlines have a best-price guarantee, so you shouldn t have to sacrifice a good fare. But check around to be sure. And, of course, the more miles you earn, the more they re worth.

These changes aren t a promotional thing, says Peterson. They re a permanent part of the program.

Get the code

Promotion codes are the Holy Grail of leisure travelers, Seaney says. But there just aren t typically a lot of them around -- especially for domestic airfares. Jet Blue and United publish deals on Twitter. Seaney s FareCompare.com publishes codes on a deals blog, and other sites do, as well. A simple Google search for airline coupon code can lead you to a slew of sometimes-helpful sites.

Similar to redeeming miles, these codes typically must be used on the airline s web site.

Codes tend to have a short life span. To beat the clock on coupon expirations, sign up for RSS feeds or alerts and be ready to pounce.