If you want to board your plane early in order to claim space in an overhead bin, some airlines will make you pay for the privilege. American Airlines charges for a service called Express Seats. You have to pay more for your ticket, but you can be one of the first people to board for your flight, regardless of your frequent flier status.
You also get to sit in one of the first few rows in coach. Pricing varies by trip, but The Dallas Morning News reported the surcharge at $19 to $39 each way.
JetBlue Airways recently launched a related program called "Even More Space," which costs a minimum of $10 per seat. Customers have early access to boarding and overhead bins and can sit in rows with extra legroom.
If you don't pay this extra charge, you'll have to hope you can grab a seat with sufficient space after the airline loads everyone else.