Lady you have got it. What airline are the tickets on would be my 1st question, then what are the restrictions?
The things to look for are seat pitch, that is the distance between seats and width. The remaining legacy carriers Delta, United, and American along with Southwest are fairly decent still. You pay for booze, there is no food, and expect to pay for everything. Now for the 5.5 hour flight you want to be be comfortable.
If they are a legacy pay for the Economy Comfort (Delta), or Comfort Plus (United). Look at the fare class that will tell you a story. The higher the class the higher the perks; early boarding, use of overhead bin space etc. Now the fare classes are a way of managing profits, and the fare classes are split out that way
Expect to pay to check bags, make sure your bags 23 kg or less. Look at the baggage guidlines to see what the airlines rules are.
I have seen horror stories, and read horror stories about the budget Airlines'. Think Spirit, Allegiant, Frontier and the rest. Something happens you are left to scramble, they are notorious for leaving customers in the lurch
“Better a true enemy than a false friend.”