I like Richard Branson's claim (paraphrased) that the way to become a millionaire is to become a billionaire and start an airline.
But that's a bit glib.
It's not actually that bad if your ambitions are not massive scale. There are any number of niche local airlines that have started with a couple of small/old leased planes even relatively recently. There are well established leasing mechanisms, and passenger planes have an extremely long expected lifetime but larger airlines are often under constant pressure to upgrade to bigger and more cost effective planes, and so there's a lot of supply.
In fact, there are websites where you can enquire about quotes for leasing full size passenger planes.
That business model for scheduled service is usually built around Federal government subsides to service infrequently visited airports. "Cape Air" is an example such airline that flies to places like Nantucket, MA and Lake Placid, NY. The airports often coincidentally happen to be where prominent congressmen live or have summer homes.
The other variant for that niche airline model is charter flights -- get a few hundred people from a city to go to Jamaica or something.
The delusion that some have that airlines represent "perfect competition" is amusing. It's an industry held up by direct subsidy, indirect subsidy via the Postal Service & military, and other bizarre compromises.
But that's a bit glib.
It's not actually that bad if your ambitions are not massive scale. There are any number of niche local airlines that have started with a couple of small/old leased planes even relatively recently. There are well established leasing mechanisms, and passenger planes have an extremely long expected lifetime but larger airlines are often under constant pressure to upgrade to bigger and more cost effective planes, and so there's a lot of supply.
In fact, there are websites where you can enquire about quotes for leasing full size passenger planes.