Thought getting through airport security was tough? Just try to avoid paying an added fee for your luggage these days.

As a result of skyrocketing fuel prices, United Airlines and US Airways both plan to follow American Airlines' lead. These moves come just months after six of the major airlines started charging.

"Most of the remaining airlines are probably going to jump on the bandwagon," says Ed Perkins, contributing editor for SmarterTravel.com, a travel advice site. Continental Airlines, Delta Air and Northwest Airlines have yet to rule out adding similar first-bag fees. The rare exception to the carriers' fee-centric mentality: Southwest Airlines. In what now seems to be a very prudent move, the airline locked in gas prices eight years ago, affording it the ability to be the only major airline that does not charge for either of the first two checked bags.

"[Air travel is] truly becoming an a la carte business right now," says airline expert Terry Trippler, owner of booking site TripplerTravel.com. "You're paying for the flight, and everything else is extra." (If the thought of paying to check a bag makes you reach for a stiff drink, bear in mind that US Airways will also begin charging $2 for once-free on-board beverages like sodas, water and coffee. Alcoholic beverages, previously $5, will be $7 after the new policy takes effect Aug. 1.)

With a little strategic packing and forethought, savvy travelers can send their bags packing without paying too hefty a price. Here's how:

Carry-On Bags

With airlines charging more for bags in the cargo hold, space in the cabin has become prime real estate. Airlines haven't started charging for gate-checked bags, but they're already more strictly enforcing what makes it aboard, says Doug Dyment, founder of OneBag.com, a packing advice site. Even the standard advice to pack light might not help your bag make it into the increasingly crowded cabin. Try these other tricks as well:

Embrace the middle seat: It usually has the most under-seat space, ideal for a squishable duffel, backpack or small rolling briefcase, says Susan Foster, author of "Smart Packing for Today's Traveler." (The plane's curvature reduces space under window seats, while aisle seats have condensed space to allow for wider aisles.) The catch: Some airlines store electronics or other equipment under the seat, so check with your airline first about maximum dimensions. Many offer this information outright in carry-on bag restrictions, but you can also find it in the airline's policy section on traveling with pets on-board carriers must fit below the seat.

Board early: If you're worried about getting that space in the overhead bin, know your airline's boarding routine and make sure you're among the first in line for your section. Most carriers allow passengers with disabilities and elite frequent fliers to board first. Northwest offers open boarding in no particular order, while Delta often starts with the window seats in the back.

Be aware of carry-on limits: Airlines are cracking down when it comes to carry-ons. American, for example, limits bags to 45 linear inches (length plus width plus height) and 40 pounds. It also permits one small personal item, such as a purse or briefcase. (Child safety seats, strollers, diaper bags, small bags of food, wheelchairs and walkers are exempt and may be brought on additionally.)

Checked Bags

Even if you can stomach that $15 checked bag fee, it's not the only charge you need to worry about, cautions Ann McAlpin, author of "Pack It Up: The Essential Guide to Organized Travel." Airlines charge an average of $50 for any bag that exceeds the 50-pound weight limit for domestic flights. Bags weighing more than 75 pounds rarely make it on the plane at all. The good news: It's possible to limit what you pay, or even avoid the fees altogether:

Check airline exemptions American and United waive first-bag fees for first- or business-class passengers and elite frequent fliers. All major carriers still allow two checked bags for flights with an international leg. You might also be exempt if you bought your ticket before the new fee goes into effect. US Airways won't charge those who purchased tickets before July 9. Consider planning future trips on an airline that hasn't yet announced a first-bag fee.

Note item exceptions: Most airlines allow passengers to check strollers, car seats and wheelchairs free of charge. Read the policy. Each airline has its own set of restrictions as to the number of bags, weight and dimensions, says McAlpin. Review the policy before you pack. If you're traveling on multiple airlines, make sure your bag works within the guidelines of each.

M

Start small: "The bigger the bag, the more you put in it," says Foster. Don't check a bag bigger than 24 inches if you don't want to go overweight. Large bags are just plain heavy even when empty and they also lend themselves to overpacking.

Look for a light bag: Here's one case where it works to your advantage to go with cheaper luggage. "The less you pay, the less they weigh," says Foster. Excellent craftsmanship on high-end bags weighs them down. Look to inexpensive yet sturdy lines sold at stores like Macy's and Target instead. It's not lifetime luggage, she cautions, but it should stand up to a few vacations a year.

Shipped Bags

Most luggage-shipping services will be financially out of reach for consumers. "If you're Mrs. Rockefeller, they're fabulous," says Foster. "A not-too-heavy bag sent cross country is still a couple hundred dollars." Still, there are a few cases where shipping can be the more economical choice:

Weigh the fees: Sending just the one bag doesn't make sense, but someone traveling with three or four pieces of luggage, or something bulky like sports equipment, might come out ahead, says Perkins. Checked-bag fees jump steeply at the third bag. US Airways, for example, tacks on $100 each, while United charges $125. Baggage forwarding company Luggage Free charges $82.50 to send a 50-pound bag one way via its slowest, five business-day service (the charge is $220 for delivery for its fastest one-day delivery).

Consider well-known carriers: Federal Express, United Parcel Service and the U.S. Postal Service can be even cheaper, says McAlpin. A 50-pound bag sent via UPS Ground from New York to Los Angeles costs just $59, with five days in transit.

Check with your hotel: Some hotels charge a fee to accept a package, plus more per day to hold it until your arrival, warns Trippler. The Residence Inn by Marriott Las Vegas South, for example, charges $1 per pound to accept and hold a package of 25 pounds or more. Charges like these could easily cancel out any savings you may reap through shipping.