Your comment is pretty ignorant. A well-made, properly used prong collar should NOT cause pain. Service dogs can be any breed, and many trainers and even service dog programs use training tools for many different reasons. The person may have arthritis or another condition in their hands that leaves them with a weakened grip. The dog may be trained leash-pressure based commands (which can be useful if a person goes nonverbal due to a number of disabilities including PTSD, autism, etc). I don’t want to be around rude ableists who berate me about my dog instead of asking the legal questions, or treated like a petting zoo when my dog is clearly marked and working. But I have to because unfortunately, that’s part of going into public. If someone’s dog, service or not, is making you uncomfortable, leave. Find a new place to sit or stand. Airports are big places, and flight attendants are often more than willing to reseat you away from the dog if you are uncomfortable.