Nah, you can get a small four or five seater jet (eclipse) for pretty cheap these days - https://www.controller.com/listings/aircraft/for-sale/178755.... Maintenance is expensive, but it's doable. Not saying it's a wise purchase, and not a 747, but my very conservative father-in-law is in that realm and loves flying his jet around (he lives in the middle of nowhere and owns a lot of farms, so it's almost a necessity). All in you're probably looking at $1,000/hr to fly it. But then no TSA...

That said, point taken, most people wouldn't buy a jet if their net worth was $15m. I might.