Dogs may lick the air when they are bored. This is a way for them to self-soothe and relieve stress.
Dogs may also lick the air when they are anxious. This is a way for them to try to calm themselves down.
Dogs may lick the air if they are feeling nauseous. This is a way for them to try to get rid of the feeling.
In rare cases, dogs may lick the air due to a medical condition, such as a neurological disorder or a digestive problem.
Some dogs may lick the air because they enjoy the taste of it. This is especially common in dogs who have a keen sense of smell.
Dogs may also lick the air to get your attention. If you give them attention when they do this, they may learn that it is a way to get what they want.
In some cases, dogs may lick the air simply because they are playful. This is especially common in puppies.