Just a reminder for those comparing fares on Southwest to the other airlines...if you will be checking any bags, the other airlines will charge a fee for each bag. JetBlue charges $35 for the 1st checked bag, unless you book Blue Plus or jetBlue Mint class, are a Mosaic member or a jetBlue cardholder. A 2nd bag is $45. American charges $30 for 1st bag, $40 for a 2nd checked bag, as do Delta and United; however, if you book a more expensive ticket or hold their credit card, the 1st checked bag usually is at no charge (sometimes, others under the same confirmation number receive the same no-charge checked bag perk, as well). Some airlines charge a higher fee, unless you purchase your checked bag in advance. If only flying with a carry-on, there is no fee, unless flying an Ultra Low Cost Carrier, such as Frontier. Frontier charges for a carry-on bag (does not fit under the seat in front of your seat), as well as for checked bags, unless purchasing one of their bundles, where the bag(s) can be included. A friend of mine occasionally flies Frontier, only with a small bag, which fits under the seat; sometimes, the whole fare is in the low double digits, including taxes and fees, and the actual air cost is literally pennies.
On many airlines, it's a good idea to purchase your bag fees at least one day prior to travel, for the lowest cost.
Sometimes, having elite frequent flyer status with an airline will afford the no-fee checked bag perk, as well as boarding early in the process.