Since it happened before my time in this business, I wondered what was done to allow some of the big radial powered airplanes that used what was 115/145 octane avgas that was colored purple, when 100LL was introduced? I talked with many persons who were in the military during the 50’s and 60’s who used to work with that fuel. Another suggestion about adapting high powered or turbo-charged may not be workable. Most light twins have marginal single engine climb capability and any reduction in power would result in no single engine climb at all. That would put most pt135 outfits out of business flying those planes. Switching to turbine (using jetA) would not be cheap either. I find it highly unlikely any privately owned ( not government) flight school could afford or actually make a profit on airplanes costing millions of dollars apiece (verses thousands). As far as the constitutional (5th amendment) requirement to compensate those for the government “taking” of airplanes due to leaded fuels being banned, all one has to do is look what has happened to all those businesses lost due to all of the COVID shutdowns and restrictions. As far as I know none of them have been compensated!