Why does any of this imply they should become a regulated utility? This seems like a textbook case of the free market pushing prices down to cost. Having alternative revenue streams pushed that minimal price down; but even without that, there is no reason to think the market would have done anything other than push prices to the lowest level possible in that environment as well.
Because the amount anyone would actually pay is substantially below cost for most routes, but it's still a service that many people depend on (either directly or by the indirect economic impact of travel). It's a genuine force multiplier that is unaffordable without being subsidized; making it a utility would just shift the subsidy from credit card points programs to the government.
Company makes too much money: "they're extracting monopolist rents! They need to be a regulated utility!"
Company makes too little money: "there's no money in this industry! They need to be a regulated utility!"