You might want to consider getting a different vet. Vets can make mistakes, not be up to par with knowledge... just like any Dr. If your dog isn't mentally stable enough to fly without sedation, perhaps it shouldn't fly! Perhaps if you really want to take your pet, take it in a car.
Medicating/sedating dogs in a place where you can't respond appropriately to an emergency caused by the medication (like 30,000 feet in the air!). What would you if your dog became aggressive, went into seizures, stopped breathing from a med reaction? A person really might want to consider thinking and planning for these things. Being responsible for other living creatures sometimes thinking outside the box - even if we choose not to do that for our selves in our own life.
Something very pressing for SD owners and even just pet owners is to be critical of their care. Research drugs or procedures given to your animals. Know the actions and reactions and contraindications. Check up behind vets and trainers and anyone who recommends anything for the animal. That is called being an informed consumer and responsible owner and steward for your animal. This is what we as health care consumers do for ourselves! Why would we not do that for animals or children in our care also.
Roxie