There's nothing not to love about a trip to warm, sunny Mexico – except realizing that you're going to have to pay for that checked bag full of snorkeling gear and swimsuits. The good – albeit confusing – news is that while most airlines that fly to Mexico have similar carry-on policies, the rules about checked luggage can vary quite a bit.

Checked Bag Size Limits

Unless otherwise noted, airlines allow checked bags to measure up to 62 linear inches (which means the total length plus width plus height) and weigh up to 50 pounds. Most airlines that charge a checked bag fee start at about $25 for the first bag, but fees for the second bag can vary widely. In all cases, extra fees apply for bags that are overweight or oversized, and in some cases, overweight or oversized bags will be rejected outright. Some airlines will also restrict extra bags during the winter, since this is such a popular time to visit Mexico.

Regular Carry-On Rules

It pays to pack light: Most of the airlines listed allow all travelers one free full-size carry-on bag and a small personal item. As a general rule, carry-ons can measure up to 9 by 14 by 22 inches or 45 linear inches, and the small item should fit under the seat in front of you.

Alaska Airlines Baggage Rules

Alaska Airlines charges a fee for each checked bag – unless you meet one of their waiver requirements. Strollers and car seats are allowed free of charge if you're traveling with infants or children. If you have an Alaska Airlines credit card or happen to be traveling to and from Guadalajara, you're entitled to one free bag.

You can check two free bags if you're traveling in first class, are a Club 49 member traveling to or from Alaska, or have reached an elite level of Alaska's frequent flyer program. Active-duty U.S. military and their dependents are also entitled to up to five free checked bags that can weigh up to 70 pounds each, even when traveling to a popular vacation site like Mexico.

American Airlines Baggage Policy

American Airlines' baggage policy is even more dependent on your ticket class – and loyalty tiers – than that of other airlines. To get a complimentary checked bag, you must hold gold status in the AAdvantage program or ruby status with the oneworld partnership, or have purchased a business class or premium economy seat. Everyone else has to pay for any checked bags.

Checked Bags on Delta Airlines

If you're flying to Mexico in Delta's first class, Premium Select or Delta One seats, you're allowed two checked bags of up to 70 pounds each. But for any other class, you'll have to pay a fee for each bag and stick to the usual 50-pound maximum.

JetBlue Baggage Rules

As with many airlines, the key to avoiding checked bag fees on JetBlue is joining their loyalty program. Basic "Blue" level members still have to pay a fee for every checked bag, but Blue Plus members earn one free checked bag, and Blue Flex members get two free checked bags.

Checked Bags on United Airlines

United Airlines has one of the industry's least-generous policies, requiring passengers on international flights to pay fees for both the first and second checked bags. Passengers with non-economy class tickets or who have Premier Gold or higher status in the frequent flyer program have an increased weight limit of 70 pounds per bag instead of the usual 50.

If you're traveling on a basic economy ticket without a Premier membership or MileagePlus credit card to back you up, you'll also have to gate-check your full-size carry-on and pay an extra fee for it, on top of the usual checked bag fee.

Southwest Airlines Checked Bag Policy

On Southwest Airlines, you can check two bags free of charge as long as they're under the usual size and weight allowances. You can also carry on slightly larger bags than usual, up to 10 inches by 16 inches by 24 inches.

Baggage Rules for Spirit Airlines

Spirit Airlines serves just a couple of destinations in Mexico, and it's best for those who pack light. The only luggage included in your basic ticket is a personal item, like a laptop bag or a purse. You'll have to pay a fee for larger carry-ons and checked bags.

Sun Country Airlines Baggage Policy

Although Sun Country Airlines has a relatively small footprint in the United States, they service quite a few destinations in tropical countries like Mexico. For destinations outside the contiguous 48 U.S. states, they offer several luggage options. The Grab & Go option includes only a small personal item that you carry on the plane, and it's the only free option. Check & Go includes one personal item, no carry-ons and a single checked bag. Store & Go includes a personal item and either a carry-on, which can measure up to 24 inches by 16 inches by 11 inches, or a checked bag. First-class tickets qualify you for a free personal item, carry-on and two checked bags.