Hi Malabo,
It's mostly (but not entirely) accurate that the airline industry owns nothing, albeit the portion of leased (incl financed) vs owned outright is skewed heavily in favour of financed/ leased. Covid accelerated the trend away from owning as airlines preserved cash as best they could. Covid was a bonanza for patient leasing companies. The generally accepted portion of owned outright in the airline industry now is about 20% so very low.
On the rotary side, in terms of oil companies buying assets for others to operate, it's not really been done as far as I'm aware, certainly not at scale: I think Chevron bought some 429s in Angola for Heli Malongo years back but I might be wrong. There are plenty of examples of oil companies buying aircraft but then also then operating them in house. Exxon own their 139 fleet in Australia but also operate them, BSP same. There are others of course. I'm still not convinced Equinor will actually buy these assets in the end, the oil company might have just placed the order and will then sell the slots to a finance company elsewhere at a later date on the quiet.
I can't see the finance teams in oil companies being excited about buying helicopters and having them on these assets on their balance sheet. I think Equinor just wanted to kick start the move to a new type so did this knowing the market could/ would likely take care of the financing down the line. I suspect there are also ways for Equinor to get out of the deal if the aircraft is not certified by a certain date or there is a minimum guaranteed performance clause (ie if Equinor cannot move X people X distance offshore in X weather then Equinor can walk).