Spirit Airlines has a missed flight policy outlining the rules and fees associated with missing a flight. Here are the key points to keep in mind:

1. No-show fee: If you don't show up for your flight and haven't canceled or changed your reservation beforehand, you will be charged a no-show fee. The fee varies depending on your itinerary but can be up to the full fare of your flight.
2. Rebooking: If you miss your flight but contact Spirit Airlines within 24 hours of your scheduled departure time, you may be able to rebook your flight for a later date. However, you will likely be charged a rebooking fee and any fare difference.
3. Standby: If you miss your flight and arrive at the airport, you can fly standby on a later flight for a fee. The fee varies depending on your itinerary and whether you're a Spirit's $9 Fare Club member.
4. Refunds: Spirit Airlines typically does not offer refunds for missed flights unless there are extenuating circumstances, such as a medical emergency.
5. Check-in time: It's important to note that Spirit Airlines has strict check-in deadlines, and if you don't check in before the deadline, you may be considered a no-show and charged the appropriate fee. The check-in deadline is typically 60 minutes before domestic flights and 90 minutes before international flights.

Overall, it's essential to read and understand Spirit Airlines' missed flight policy before booking your flight and to ensure you allow plenty of time to check in and arrive at the airport before your scheduled departure time.