Just like the official carry-on size seems to change every day and varies between airlines, baggage fees are murky, inconsistent, and difficult to navigate.

We investigated how much 9 major US airlines charge for checked bags and created a handy guide to airline baggage policies to help you avoid costly surprises.

Spirit charges guests the most for checked bags, closely followed by Frontier.

Your best bet is Southwest, which doesn't charge for carry-on bags or the first two checked bags. Jetblue only charges for one checked bag ($20) and Alaska charges for two checked bags ($25).

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