You 'can' lease the DC-3 from older accounts that you not use anymore.
So if any day for any reason you got bankrupted and registered again to have another chance with another company, in this round, as you can not manage more than one account, you choose one and use the others to lease their initial aircrafts to you.
A suggestion... some accounts must be closed if there is no login or any change in a determined period of time.
That would be cheating to creat accounts and give away super cheap leases.
I mean, it would be kind of obvious too, especially if it's a new airline with only one plane that suddenly leases a plane for $1000 or even $5000. It makes no sense as they won't be making enough money from that to even purchase a new plane for a long time. A route that isn't even full will bring in more money than that in a day. The cheapest plane right now is 1.1 million. That means it would take 220 real time days at $5000 a month to get enough money to purchase another plane.
Even so, two accounts on the same IP that are leasing planes to each other should be a sign of cheating.