Once viewed as little more than refueling and maintenance stopovers, fixed-base operators (F.B.O.) are being transformed from facilities with spartan waiting rooms and drip-coffee machines to ultra-swank private enclaves. Clay Lacy Aviation’s new complex at John Wayne Airport in Orange County, Calif., for example, spans 41,800 square feet of office and terminal space, with garden-accented lounges and 145,000 square feet of hangars. On a more intimate scale, the Coeur d’Alene airport in Idaho is home to StanCraft’s Jet Center, designed by an internationally renowned wooden boatbuilder and pairing modern F.B.O. conveniences with rustic spaces such as the Hardwood Coffee Café. These enhancements are being driven by increased demand for private jets alongside rising expectations from customers seeking five-star services. According to the Insight Partners, a New York–based research firm, the global F.B.O. market will grow from $25.55 billion last year to $41 billion by 2031. In response, today’s most sophisticated facilities offer spa-like..