"The sky was clear that morning, the wind light."
Note the words "that morning"
i.e. it was clear and light at the time and place he took off. Later in the day, thunderhead activity over the mountains was severe. If a little plane flew into a "canyon" between rows of thunderheads, and then it closed, the odds would be slim indeed.
Weather requires respect, for both small and large planes.
Man was never meant to fly, yet Ecco Si Muove