W illiam A. "Bill" Franke is an American billionaire who is a pioneer and a major power broker in the global low-cost airline industry. After a successful career as the CEO of a major regional bank and an airline, he founded the private equity firm Indigo Partners in the late 1990s. Indigo specializes in investing in and developing ultra-low-cost carriers (ULCCs) around the world. His strategy is to acquire or take controlling stakes in budget airlines and then apply a rigorous, disciplined formula of extreme cost-cutting, high aircraft utilization, and charging for every ancillary service to achieve profitability.

He has successfully applied this model to a portfolio of airlines across the globe. Indigo Partners is the controlling shareholder of the American ULCC Frontier Airlines, the European carrier Wizz Air, Mexico's Volaris, and Chile's JetSMART. Franke's biggest and most famous deal came in 2017 when he orchestrated a record-breaking order for over 400 Airbus A320neo family aircraft for his portfolio of airlines, one of the largest aircraft orders in history. He is considered one of the most influential and successful figures in the modern aviation industry.