How many hours per year are you looking at? Considered chartering? NetJets, FlexJet, ExecuJet etc etc... This option would not require you to "lock" any cash. Reading your posts you give the impression that with cash on hand you could easily make enough returns on invested money to make up for increased fuel burn, maintenance etc .... How about investing the equivalent of a Challenger, in the price range you mentioned and aim for 15% (I have no clue) return? This would leave you with $600 000 + to spend on chartering an aircraft, no maintenance hassle, no crew to pay, no hotels for crew etc etc...
CP