Well, I've watched that scene in the movie several times and never seen a dog. Perhaps someone can post a clip and prove me wrong. If not, QED.
And what does "no dog known to exist on the airfield" signify? If a dog runs into a park and the people there were not aware of the fact it does not even start to mean it is a ghost. What a daft statement.
Quite apart from the daftness of believing in ghosts. Now that's a worry.
Hooey!