As you are/used to be an air force guy...I read once that it might be a good idea to put more effort in putting turboprop planes back into the air.
Energy-wise this technology could be made a lot less wasteful than current jet engine tech. As it currently stands the two technologies match each other.
Besides this, commercial airliners fly as slow as they can get away with already for years now, to keep fuel costs down. Almost negating the advantage a jet has over a turboprop (speed).
From that article I understood that using similar maintenance procedures/intervals for turboprops as is done for jets, current turboprop tech is as reliable and almost as fast current jets fly, but a lot cheaper with fuel.
I keep saying article, but it could also have been a paper or case-study...