Air Mail Route 78 was one of the first post-war feeder routes to be inaugurated. Service was originally scheduled to start on September 18, 1946, but was postponed for ten days. The airports at Burley, Twin Falls, and Pullman / Moscow were not ready for the inaugural service. 

This cover was carried on the inaugural Air Mail Route 78 flight from La Grande, Oregon to Spokane, Washington (where it was backstamped) and is listed in the Contract Air Mail Flights (CAM) Section of The American Air Mail Catalogue as 78N7.

Effective June 27, 1952, Empire Air Lines was merged with West Coast Airlines.

The Civil Aeronautics Board and President Lyndon Johnson approved the first-ever simultaneous merger of three airlines in early 1968. Pacific Air Lines, Bonanza Airlines, and West Coast Airlines were combined to form Air West. Air West provided service to eight Western states, Canada, and Mexico within its 8,800-mile system.

In 1970 Howard R. Hughes and his Hughes Air Corporation acquired Air West and the name of the carrier was changed to Hughes Air West in April. In 1971 the name was changed to Hughes Airwest.

Effective on October 1, 1980, Republic Airlines, Inc. purchased Hughes Airwest and made the carrier a wholly-owned subsidiary known as Republic Airlines West, Inc.

On January 23, 1986, Northwest Airlines announced an $884 million purchase of Republic Airlines, the biggest merger in U.S. civil aviation history. The two carriers filed a merger application with the Department of Transportation on January 27. The Justice Department opposed the merger because it would “substantially lessen competition” in violation of antitrust laws. Full hearings regarding the merger were held and on July 31 the Department of Transportation approved Northwest Airlines’ takeover of Republic Airlines. On August 12 the acquisition of Republic was completed as officials from both airlines transferred ownership of Republic to Northwest. On October 1, 1986, the operations of Republic were fully integrated with a single Northwest flight schedule.

On April 15, 2008, Delta Air Lines and Northwest Airlines announced a merger agreement. The merger of the two carriers formed what was then the largest commercial airline in the world, with 786 aircraft. Delta Air Lines' brand survived, while Northwest's brand officially ended in 2009.