Joe Sprague left Alaska Air Group Inc. on Sept. 1 after 17 years with the airline, the company said Monday.

SeaTac-based Alaska did not explain the senior vice president of external communications’ departure, but announced the hiring of former Kaiser Permanente executive Diana Birkett Rakow as vice president of external relations.

Sprague could not be reached for more information. His LinkedIn account says he “retired” from Alaska Airlines, but added that he already has a new job.

Sprague will…