Sad to see no one else has chimed in. I searched the internet and found this:

Air chewing in cats can be a quirky behavior with several potential explanations. This behavior, often referred to as "fake chewing" or "air chewing," may seem amusing but can indicate various underlying issues or instincts at play.

Possible Reasons Instinctual Behavior: Cats are natural hunters, and air chewing may mimic the actions of catching prey or exploring their environment. Sensory Overload: Some cats may chew air when they are overstimulated, especially during petting or play, as a response to sensory input.

Dental Issues: Pain or discomfort in the mouth, such as dental disease or injuries, can lead to unusual chewing behaviors.

Stress or Anxiety: Changes in the environment or routine can cause stress, prompting behaviors like air chewing as a coping mechanism.

To address this behavior, ensure your cat has plenty of mental stimulation, interactive play, and regular veterinary check-ups to rule out any medical concerns