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I've read that turbo-prop aircraft are more efficient than jet-aircraft. Browsing this Wikipedia page it looks like in general, jet airliners burn less fuel per passenger. I imagine this is due to jet aircraft typically carrying more people, and flying longer in cruise. Is there some fundamental reason why traditional propeller designs couldn't be scaled up to 150+ passengers and trans-oceanic ranges? If it was possible, would air travel become substantially more efficient per passenger?
Edit: Perhaps a better phrased question would be: are turboprop aircraft always more efficient, regardless of airframe size? Or is there some regime where modern turbofans take over? I'm specifically asking about fuel efficiency (i.e. ignoring noise / speed).