Krusty, I don't pretend to know much about corporate finance but my understanding is that if REX has a D/E ratio of 5% then that means that they are missing out on some tax benefits - I believe that 45% is about optimum between keeping the debt at a manageable level versus getting good taxation advantages.
If DJ were to get Turboprops, that would be an admission that they got it wrong when they purchased Embraers in response to QF Link's purchase of Dash 8-Q400's. A number of PPRuNers claimed at the time that the DJ Embraers would dominate the market because of the pax preference for jets. From what has happened over the last few years, it appears that pax are still very price sensitive and that Turboprops are significantly cheaper to operate than Jets.