To keep ticket prices (Bare Fare™) low for everyone, SpiritAirlines charges for carry-ons and checked bags. SpiritAirlines charges more for checked bags over 40 lbs. This is because the added weight requires more gas for the plane. One personal item that fits entirely in the smaller sizer box (like a purse, small backpack, etc.) is included with your ticket. Another personal item or anything larger like a standard carry-on or checked bag will need to be paid for.
PRO TIP: If you know you’re going to need a carry-on or a checked bag, buy it right when you book your flight to save major moola.