Tri-Jet will return one day......
They will have to replace quad with Tri one day anyhow. Twin engine, itself, have proven it's limitation while quad have proven the more flexibility. One will have to make Tri to replace quad engine when energy conservation become too sarfice, Just like back in 70's. Or to increase the air speed and reduce operation costs. That is the what it should be by time we become an elderly anyway.
Ask yourself will we see 500-600 mph (On long range flights) for the rest of our life? I doubt that.
That's my take......
