Co-branded credit card revenues are a highly attractive, underappreciated profit stream for airlines. They are growing at a low double-digit CAGR, contributing a low double-digit percentage of overall revenues, with estimated operating margins of 35-50% or higher. This business provides stability and could represent roughly half of midcycle airline profitability. Travel has become a consumer staple spending item, supporting continued growth in travel spend and co-branded card usage, making the airline industry a beneficiary of this durable ancillary revenue stream.