Complex sentence: In addition to a check up the dogs are also spayed, neutered, and vaccinated then when a dog is finally well enough to travel volunteers in Puerto Rico help prepare the dogs to fly to either JFK National Airport or Newark Airport.
Split into simpler sentences: In addition to a check up the dogs are also spayed, neutered, and vaccinated. When a dog is finally well enough to travel, volunteers in Puerto Rico help prepare the dogs to fly to either JFK National Airport or Newark Airport.