--- and just to add to John's comments -- the Wrights didn't have a machine that could fly away by itself & kill some unsuspecting individual many miles away (or more likely in the case of Barwelle's model, some nearby unsuspecting individual -- such as himself).

Back to the flight-time issue. A very general rule of thumb (with due deference to Campy for stealing his line) is 1 min/oz for a .60 size engine, 1 1/2 min/oz for a BB .46 size engine & 2 min/oz for a .40 size bushing engine -- this is from start-up & includes taxiing & landing. This will vary with engine manufacturers, altitude, weather conditions & nitro content in the fuel -- high-output engines, low altitude, cool weather & more nitro = less time.