3) Is implemented in a socialist model. Government creates a public company behind it, provides some of the initial investment, privates provide the rest; price

3) Is implemented in a socialist model. Government creates a public company behind it, provides some of the initial investment, privates provide the rest; prices maintain to help pay for it (+ private quota), even though costs were cut significantly; decrease/fluctuate prices over time to match costs (maintenance, fuel). You got yourself a national fleet. Note, that my comment does not necessarily has the US in mind.