I think it's fair enough for mini horses to be allowed where legitimate service animals are allowed, generally. They are better than dogs in many ways. However, I don't think they should be allowed on planes for safety reasons. Those things weigh over 100 pounds and have sharp hooves. Have you ever been on a plane when it goes through bad turbulence, the kind where you will hit your head on the ceiling if you don't have your seatbelt on?
I have to put my laptop away during landing for legitimate safety reasons of avoiding heavy things flying around the plane in case of accident. But I'm supposed to believe this horse just standing there is safe?
Until they figure out a restraint for them I will not fly if I have to sit near one.