The fare at the airport equaled the online fare minus the $19 CIC, but the lady at the ticket counter told me that she has to tack on the $25 airport purchase fee on top of the fare. I couldn't find anything on the website that said anything about this fee, and asked to speak with her manager. The manager confirmed that yes, all ticket purchases at the airport incur a $25 fee which is in addition to the base fare/taxes. I did not have a promo code. I called the call center and the guy told me that the $19 CIC was a government-imposed tax, which of course is not true, so I asked to speak with his supervisor, who said that only the airport could waive the CIC, and was not sympathetic to my concern that it seemed impossible for me to purchase a ticket without some carrier-imposed fee. It was all rather odd. I think I'll write to Frontier to see if they can clarify with me and/or the airport staff (I was at ORD). Because the $25 fee I was quoted was higher than the $19 CIC online, I did not purchase the ticket at the airport.