It took a lot of web searching, but I found it. Having grown up watching Sky King flying out of the clear blue of the western skies, I raked my brain trying to remember a dog on the show. I could remember Rin Tin Tin, Sgt. Preston's dog King, Bullet running alongside Roy Rogers, but no dog jumping down from an airplane. Thank goodness other people's memories are better.
A white german shepard, he belonged to Penny, and his name was 'WHITE SHADOW.'
A beautiful animal, and Penny called him 'Shadow' for short.