Airline baggage rules for Spirit Airlines are designed to keep fares low while giving passengers flexibility. Each passenger is allowed one free personal item, like a small backpack or purse, that fits under the seat. Carry-on bags and checked luggage incur additional fees, with lower costs if paid for during booking. Checked bags have a 40-pound weight limit, and overweight or oversized luggage incurs extra charges. For the best value, travelers should pay for baggage early, pack efficiently, and be mindful of Spirit’s specific size and weight restrictions to avoid unexpected fees at the airport.