I've wondered about this for some time now. When flying on an IFR flight plan many times I have been given a clearance direct to a VOR that is well beyond the range of the station. Most recently, I was cleared direct Des Moines from western NE (300 some miles away) while enroute to Chicago. When I filed the flight plan, I filed as a BE-76 /A (Mode-C, DME). Now, knowing that I don't have an IFR approved GPS onboard (or knowing that I have any GPS onboard), how can ATC approve me to fly such a long direct routing that obviously can't be done with traditional VOR navigation? Is it assumed that I have plotted the course and figured out the MORA for the routing I have been given? Even so, what form of navigation (that is acceptable for IFR navigation) are they assuming I am using to navigate that route? LORAN? VOR RNAV?
Anyone with any insight?