Can I Upgrade a Seat on Spirit Airlines?

Yes, Spirit Airlines allows passengers to upgrade their seats to a higher cabin class. Moreover, there are numerous ways to make an upgrade, such as by purchasing a Spirit Big Front seat or by requesting an upgrade during check-in at the airport. Further, passengers also upgrade their seats with the help of the Spirit Airlines seat bid upgrade option, for this travelers have to place a bid of a certain amount and if get accepted, their seats will be upgraded.
Read more:
https://medium.com/@airlines-group-travel/how-does-spirit-seat-bid-work-40242b682611