A woman who says she bought a ticket on the Spirit Airlines website showed up at the airport to be told at check‑in that she didn’t have “the correct fare” and that she had to pay an additional $306 to fly.

Post‑purchase price increases are generally illegal.

• 14 C.F.R. §399.88: It’s an unfair/deceptive practice to increase the price after purchase unless the increase is due to a government‑imposed taxes or fees disclosed at purchase, where the consumer affirmatively agreed to it. Asking for $306 more at check‑in after a purchase is exactly the kind of behavior this was designed to prohibit.

• Since 2015, DOT has chosen not to enforce this rule when airlines cancel mistake fares if they refund the ticket and reimburse reasonable out‑of‑pocket costs incurred in reliance on the purchase. That policy does not support demanding more money at the counter. If Spirit’s position is “that fare was a mistake,” the compliant remedy is refund + reimbursements, not “pay $306 now.”

• However, fares “are subject to change until purchased” (language from Spirit’s Contract of Carriage). Once purchased and you hold a “confirmed reservation,” you’re entitled to transportation.

The only way to ask for ‘more money’ is if no money had been collected. If payment failed, a reservation might have been created but no valid payment was captured. Usually the reservation will cancel out after a short period of time. So the airline would seek to sell the passenger a ticket. Another scenario would be a credit card chargeback.

If a travel agency, such as Expedia, screwed up ticketing that could also be an issue but here it’s a purchase on Spirit’s website. If they failed to notify the passenger of a ticketing problem, that’s on them.

Commenters suggest buying at the counter next time because of the savings that brings with carriers like Spirit, Frontier and Breeze.

• Spirit charges up to $27.99 per segment as a ‘passenger usage charge’ buying tickets online.
  
• Really, that’s part of the fare. But by calling it a fee, they avoid paying the 7.5% excise tax on domestic airfare. It’s tax arbitrage. To call it a fee, they need to offer a way to avoid paying it, hence airport ticketing – too costly and time-consuming for most to bother with, but technically compliant.

• Here, though, the issue isn’t the fee it’s that the ticket didn’t get properly issued.

The customer here should be filing a DOT complaint… although you have to hope the complaint gets resolved while Spirit is still in business.