As a companion of both a German Shepard and a Labrador Retriever, allow me to correct this statement. While German Shepards are fiercely intelligent (for a dog ) and often used as service dogs, they are typically employed as police and fire dogs, as well as used in various military roles. Labradors and Goldens are far more often used as guide dogs for the blind than German Shepards, who tend to be a little more high strung than labs or goldens.

Both, however, would readily lie in front of a moving locamotive for someone they care about. Squeezing into a tight spot would be nothing. The four or five times I have actually seen a service dog on a plane, they are generally in a bulkhead seat, and often the seat next to the human passenger is kept empty. In fact, the very first time I flew FC was about 10 years ago, when I had a bulkhead seat next to a blind gentleman, whose dog was sitting at my feet. They bumped me into FC to give the dog and me a little more space.