The industry is obviously more than 2 companies. Boeing, Airbus, Embraer, Bombardier, and likely in the future, Comac, Mitsubishi, and UAC. This is ignoring the (primarily) civil aviation companies, military manufacturers (who sometimes venture into commercial, e.g., Lockheed's Tristar), and the entire supply chain that feed into those manufacturers.
In some ways this doesn't matter that much (since these planes might actually do many more takeoffs and landings per day/week/lifetime and have to be engineered for that), but in other ways it does matter a lot.
As for the other companies you name, I will admit I am not familiar with them. Is there something relevant to add to the discussion from those companies? I would be curious to learn more
Using seat-miles leads to some very strange conclusions. Consider cargo aircraft with zero seats, or a helicopter that mostly hovers in place all day.
Aviation safety primarily looks at airframe hours and pressurization cycles. At least on the mechanical side.
Like, you take up a seat, so if you were to randomly select a mile that you've traveled in your life, what are the odds that it was on a Boeing / Airbus or a regional jet? But, I think this wasn't really clear from what I wrote