According to the "Ford's Portable Plane Car" by Jackson Smith, what caused Henry Ford to give up on light airplane manufacturing?

Question

The building materials became too costly.

He disliked the idea of "flying cars" and compared the idea to bees swarming.

His model Flying Fivver crashed on its test flight, killing his friend.

He thought affordable "flying cars" were unrealistic and predicted they would never come to be.

Answer 1

His model Flying Fivver crashed on its test flight, killing his friend.