sentences:  His aircraft was witnessed climbing to altitude, before drifting down like a falling leaf, and gliding to a landing, which was controlled enough to leave skid marks, but rough enough to rupture the fuel tank and ignite the aircraft.Hypoxia was suspected among other reasons for the crash, but the fire made it impossible to verify the exact cause.On June 18, 1988, the Grinnell Regional Airport was dedicated and named Billy Robinson Field.