Possible Clues:

• Aerial combat between fighter planes of canine origin
• Boxer rebellion?
• Mutt left out of RAF unit's encounter
• Contest for boxers maybe
• Canine conflict or combat between fighter planes
• Battle between planes
• A clash between boxers, a scrap that's up in the air?
• It's cause a bone of contention?
• Encounter that's not just pettish?
• Conflict in the air, a clash between setters, perhaps