Top 5 Tips for Keeping Your Carry-on Bags Free

U.S. baggage fee revenue dropped slightly last year, according to the U.S. Bureau of Transportation Statistics. U.S. airlines collected only $3.36 billion in baggage fees in 2011, compared with $3.40 billion in 2010. From 2007 to 2010, baggage fee revenue grew at a compounding rate of 94.11 percent each year. The sudden halt in growth in 2011 is significant for U.S. airlines. Ancillary fees, such as baggage fees, have represented a golden turnaround opportunity for airlines plagued by heavy losses. For others, fees have fueled profitability. In either case, airline fees are here to stay.

However, travelers have become increasingly savvy in avoiding airline baggage fees. As a result, U.S. airlines must be even more creative in how they charge fees. In recent months, airlines have focused efforts on generating fee revenue from carry-on bags. Here are the top five tips to ensure your carry-on bags continue to fly free:

1. Don't fly Spirit Airlines or Allegiant Air.

Spirit and Allegiant have been the most brazen, directly charging travelers to carry on a bag. The movement, initiated by Spirit, was adopted by Allegiant earlier this year. Allegiant charges $35 each way to carry on a bag, while Spirit charges $40 each way (discounts are available on both airlines if you purchase this service in advance online). Spirit has announced it will increase the fee to $50 each way starting in November. None of the other major U.S. airlines directly charge fees to carry on a bag.

2. Know the difference between a personal bag and a carry-on bag.

While Spirit and Allegiant charge fees for carry-on luggage, they do not charge fees for bringing aboard a personal bag (also referred to as a personal item). None of the major U.S. airlines charge a fee for a personal item. A personal item is smaller in size than a carry-on and must fit under the seat in front of you. A laptop bag and purse are common examples of a personal bag. While personal bags can come in many forms, only one is permitted in addition to a carry-on. If you have a carry-on bag, a purse, and a laptop bag, airlines often request that your bags be consolidated to meet the requirements of a carry-on bag and a personal bag. If you cannot consolidate your bags, you may be required to check one of your bags (see Tip #4 for more details).

3. Keep in mind various carry-on size restrictions by airline.

Both personal bags and carry-on bags are subject to size (and in some cases, weight) restrictions. It is important to note that restrictions for personal bags are different than those for carry-on bags. Moreover, restrictions also vary by airline. Unfortunately, this means that one carry-on bag may not work for all airlines. Make sure you look up the size and weight limitations for the airline you are flying in advance. Here is a carry-on luggage size chart that breaks down each airline's restrictions by personal bag and carry-on bag.

4. Be aware of extra fees if you have to check your bag at the gate

While most airlines do not currently charge a specific carry-on baggage fee, many airlines will charge you a fee to check your bag at the gate. If you forget to do the research in advance (or overstuff your bag), you may have to check in your bag at the last minute. Airtran, American, Frontier, Hawaiian, JetBlue, United, and US Airways do not charge gate-checked bag fees. For the airlines that do charge a fee, the best case scenario is that they will simply extend their standard checked bag policy, meaning you would simply have to pay the same fee you would if you were to check a bag at the counter upon check-in. However, some airlines will charge you a higher fee to check your bag at the gate. Alaska, for example, charges $25 each way to check a bag at the gate compared to $20 each way (for your first checked bag). Spirit charges $45 each way at the gate compared to $38 each (for your first checked bag).

5. Take note of extra items that can be carried on.

If your bag meets the size restrictions but is a bit overstuffed, it is important to know which items airlines allow passengers to carry on in addition to the standard personal bag and carry-on bag. These additional items vary based on the airline, so doing your homework is advisable. However, there are few items that are generally accepted across most major airlines. Reading material, crutches or walking aids, coats or jackets, food (even a bag of food), and umbrellas can be removed from baggage and carried on separately.

Alicia Jao is the VP of Travel Media at NerdWallet, which recently launched a tool to compare airline baggage fees and help you save money on air travel.