The owners generally transfer some of their personal assets to the business entity and receive some share of the business, often somewhat relative to the amount of assets they provided to the business (other assets such as talent, personal networks, etc. are not as tangible but still factor into the share each person gets).

Exactly same it works here. You could add something to the "authorized capital" of enterprise anything you want as owner. Even do that not only at moment of business creation. But you (or your business entity) become an owner or co-owner of that business.

Theoretically, yes, I just looked into our laws, one business could "invest" something into another business "authorized capital", and yes, you will not pay any taxes for such "ownership transfer". But, as side-effect, first business will become a co-owner of that another business proportional to the share of "investment" among total "authorized capital".

Also, just a note, when selling the plane, there are not necessarily tax implications. If you have been amortizing your expense claims based on the expected lifetime of the asset, then you have only paid taxes on the depreciated value of the asset, and the sale amount is likely the remaining value on that asset, and therefore no profit and thus no taxes on that sale.

Here we have something similar. You could "write off" some equipment or adjust its price in business assets balance proportional to the part of manufacturer declared lifetime that passed.

Also, you could theoretically sell something below market price but that makes sense only if you pay taxes from profit (13%), not from turnover (6%) - we have both options for LLCs and other types of businesses. And it could attract unnecessary attention from tax agency, especially if it was something expensive. Not fatal, and could be settled, but unpleasant.

Interesting, thanks for clarifications. I appreciate your patience.