groups such as california-based wings of rescue or south carolina-based pilots n paws , recruit pilots to volunteer their planes , fuel and time .
the two non-profits say their concept has been a roaring success with the numbers increasing year-on-year .
all dogs have to be spayed or neutered , microchipped and vaccinated before they take off .
it 's reported that most pooches sleep in the air and do n't get sick .