Most airlines (except Spirit) allow a carry-on and personal item. The carry-on generally goes in the overhead, and is roughly 22'' by 9'' (45 total) and weighing no more than 40ish lbs (that's super heavy for a carry-on if you get that weight), and the personal item can be a small backpack or laptop bag or something that will fit underneath the seat in front of you. Keep in mind if you get a first row seat, that you may have to put everything up top.
As for Spirit, try to wear as much of the things as possible. They apparently charge for carry-on by weight, so be careful. I have never and will never fly Spirit for this reason
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