Disney failed to properly vaccinate the original 20 puppies that they hired for filming eventually leading five of the puppies dying after contracting parvovirus. One of which reportedly died after being given back to its owner.
In the airplane scenes, you can see a mountain in the distance with snow on top. That mountain is actually Mount Baker. The mountain is situated east of the Bellingham / Mount Vernon area (on the way to the North Cascades) and can be seen in the distance on a clear day.