One correction: start with a rental price on the high side. An old rule-of-sales I learned years ago was that it is better, for psychological reasons, to err on the high side and adjust prices downward than trying to raise prices.
There should at least be airplanes that rent out that have comparable fixed costs. The idea is to figure out at least what the market has found the optimum point on the price demand curve for airplanes with similar costs.
If that is too abstract, how about trying $140/hr and see if anyone bites?