Spirit Airlines offers passengers the chance to place a bid for seat upgrades through a bidding system. After booking a flight, you will be allowed into the bidding process, where you can place an offer for a seat upgrade to Spirit’s Big Front Seat, which offers additional legroom and ease. Your bid is considered based on seat availability and how competitive it is with other offers. Spirit Seat Bid allows travelers to get a better seat at a lower price than paying outright for an upgrade. The process is simple, and the airline will notify you if your bid is successful, typically before your flight date.