Technically, a person holding only a Private Pilot Certificate cannot act as the "Pilot in Command" (PIC) of a Boeing 737 for any commercial operation, but they could theoretically fly one if they met several massive hurdles. First, any aircraft weighing over 12,500 pounds requires a specific "Type Rating" (e.g., a B-737 rating), which requires rigorous training and a checkride in a multi-million dollar simulator. Second, because the 737 is a "large aircraft" and a turbojet, the FAA (and most global agencies) requires the pilot to hold at least a Commercial Pilot License or an Airline Transport Pilot (ATP) certificate to operate it in a way that carries passengers for hire. If a billionaire private pilot bought a 737 for personal use, they would still need the Type Rating and likely a second-in-command, as the 737 is not certified for single-pilot operation. So, while a private pilot could own one and fly it with the right ratings, the vast majority of 737 pilots are professionals with thousands of hours of experience and advanced commercial certifications.